Question 1: Palette 1/132

NEET 2026 MCQ

In the first excited state of hydrogen atom, the energy of its electron is -3.4 eV . The radial distance of the electron from the hydrogen nucleus in this case is approximately:

(Take $1 \mathrm{eV}=1.6 \times 10^{-19} \mathrm{~J}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$ and $\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{~N} \mathrm{~m}^2 / \mathrm{C}^2$ )

A

$2.1 \times 10^{-9} \mathrm{~m}$

B

$2.1 \times 10^{-8} \mathrm{~m}$

C

$2.1 \times 10^{-10} \mathrm{~m}$

D

$2.1 \times 10^{-11} \mathrm{~m}$

Question 2: Palette 2/132

NEET 2026 MCQ

Four statements are given ( $A$ is mass number):

A. The volume of a nucleus is proportional to $A^{1 / 3}$.

B. The volume of a nucleus is proportional to $A$.

C. The difference in mass of an atom and its nucleus is called the mass defect.

D. The difference in mass of a nucleus and its constituents is called the mass defect.

Choose the correct answer from the options given below:

A

A and C are true, but B and D are false

B

B and C are true, but A and D are false

C

A and D are true, but B and C are false

D

B and D are true, but A and C are false

Question 3: Palette 3/132

NEET 2026 MCQ

An unknown nucleus has a nuclear density of $2.29 \times 10^{17} \mathrm{~kg} / \mathrm{m}^3$ and mass of $19.926 \times 10^{-27} \mathrm{~kg}$. Its mass number $A$ is approximately:

(Take $R_0=1.2 \times 10^{-15} \mathrm{~m}, 4 \pi=12.56$ )

A

12

B

20

C

16

D

19

Question 4: Palette 4/132

NEET 2026 MCQ

Consider that an electron is revolving in an excited state of Hydrogen atom with velocity $\sqrt{25.6} \times 10^5 \mathrm{~ms}^{-1}$. The radius of the orbit is $x \times 10^{-9} \mathrm{~m}$. The value of $x$ is:

[Take the mass of electron to the $9 \times 10^{-31} \mathrm{~kg}$, charge of electron $=-1.6 \times 10^{-19} \mathrm{C}$ and $\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{Nm}^2 \mathrm{C}^{-2}$ ]

A

1

B

4

C

3

D

2

Question 5: Palette 5/132

NEET 2026 MCQ

Consider the following nuclear reaction

$ { }^{238} \mathrm{U} \longrightarrow{ }^{234} \mathrm{Th}+{ }^4 \mathrm{He} $

Take masses of ${ }^{238} \mathrm{U},{ }^{234} \mathrm{Th}$ and ${ }^4 \mathrm{He}$ as $238.050 \mathrm{u}, 234.043 \mathrm{u}$ and 4.003 u , respectively. The $Q$ value for the reaction, in keV, is:

[Given: $1 \mathrm{u}=931.5 \mathrm{MeV} \mathrm{c}^{-2}$ ]

A

3740

B

3726

C

3730

D

3736

Question 6: Palette 6/132

NEET 2026 MCQ

In Geiger-Marsden experiment, the number of scattered $\alpha$-particles $N(\theta)$ is plotted as a function of scattering angle $\theta$. Which of the following options represents the correct plot?

A

B

C

D

Question 7: Palette 7/132

NEET 2025 MCQ

A particle of mass $m$ is moving around the origin with a constant force $F$ pulling it towards the origin. If Bohr model is used to describe its motion, the radius of the $n^{\text {th }}$ orbit and the particle's speed $v$ in the orbit depend on $n$ as

A

$r \propto n^{2 / 3} ; v \propto n^{1 / 3}$

B

$r \propto n^{4 / 3} ; v \propto n^{-1 / 3}$

C

$r \propto n^{1 / 3} ; v \propto n^{1 / 3}$

D

$r \propto n^{1 / 3} ; v \propto n^{2 / 3}$

Question 8: Palette 8/132

NEET 2024 MCQ

The spectral series which corresponds to the electronic transition from the levels $n_2=5,6, \ldots$ to the level $n_1=4$ is

A

Pfund series

B

Brackett series

C

Lyman series

D

Balmer series

Question 9: Palette 9/132

NEET 2024 MCQ

Water is used as a coolant in a nuclear reactor because of its

A

high thermal expansion coefficient

B

high specific heat capacity

C

low density

D

low boiling point

Question 10: Palette 10/132

NEET 2024 MCQ

Some energy levels of a molecule are shown in the figure with their wavelengths of transitions. Then :

A

$\lambda_3>\lambda_2, \lambda_1=2 \lambda_2$

B

$\lambda_3>\lambda_2, \lambda_1=4 \lambda_2$

C

$\lambda_1>\lambda_2, \lambda_2=2 \lambda_3$

D

$\lambda_2>\lambda_1, \lambda_2=2 \lambda_3$

Question 11: Palette 11/132

NEET 2024 MCQ

Select the correct statements among the following :

A. Slow neutrons can cause fission in ${ }_{92}^{235} \mathrm{U}$ than fast neutrons.

B. $\alpha$-rays are Helium nuclei.

C. $\beta$-rays are fast moving electrons or positrons.

D. $\gamma$-rays are electromagnetic radiations of wavelengths larger than $\mathrm{X}$-rays.

Choose the most appropriate answer from the options given below :

A

A, B and C only

B

A, B and D only

C

A and B only

D

C and D only

Question 12: Palette 12/132

NEET 2024 MCQ

Given below are two statements:

Statement I: Atoms are electrically neutral as they contain equal number of positive and negative charges.

Statement II: Atoms of each element are stable and emit their characteristic spectrum.

In the light of the above statements, choose the most appropriate answer from the options given below.

A

Both Statement I and Statement II are correct

B

Both Statement I and Statement II are incorrect

C

Statement I is correct but Statement II is incorrect

D

Statement I is incorrect but Statement II is correct

Question 13: Palette 13/132

NEET 2024 MCQ

Match List I with List II:

	List I (Spectral Lines of Hydrogen for transitions from)		List II (Wavelengths (nm))
A.	$ n_2=3 \text { to } n_1=2 $	I.	410.2
B.	$ n_2=4 \text { to } n_1=2 $	II.	434.1
C.	$ n_2=5 \text { to } n_1=2 $	III.	656.3
D.	$ n_2=6 \text { to } n_1=2 $	IV.	486.1

Choose the correct answer from the options given below:

A

A-II, B-I, C-IV, D-III

B

A-III, B-IV, C-II, D-I

C

A-IV, B-III, C-I, D-II

D

A-I, B-II, C-III, D-IV

Question 14: Palette 14/132

NEET 2024 MCQ

$ { }_{82}^{290} X \xrightarrow{\alpha} Y \xrightarrow{e^{+}} Z \xrightarrow{\beta^{-}} P \xrightarrow{e^{-}} Q $

In the nuclear emission stated above, the mass number and atomic number of the product $Q$ respectively, are

A

280, 81

B

286, 80

C

288, 82

D

286, 81

Question 15: Palette 15/132

NEET 2023 MCQ

The ground state energy of hydrogen atom is $-13.6 ~\mathrm{eV}$. The energy needed to ionize hydrogen atom from its second excited state will be :

A

$13.6 ~\mathrm{eV}$

B

$6.8 ~\mathrm{eV}$

C

$1.51 ~\mathrm{eV}$

D

$3.4 ~\mathrm{eV}$

Question 16: Palette 16/132

NEET 2023 MCQ

The wavelength of Lyman series of hydrogen atom appears in:

A

visible region

B

far infrared region

C

ultraviolet region

D

infrared region

Question 17: Palette 17/132

NEET 2023 MCQ

The angular momentum of an electron moving in an orbit of hydrogen atom is $\mathrm{1.5\left(\frac{h}{\pi}\right)}$. The energy in the same orbit is nearly.

A

$-1.5$ eV

B

$-1.6$ eV

C

$-1.3$ eV

D

$-1.4$ eV

Question 18: Palette 18/132

NEET 2023 MCQ

The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to $\left(\frac{1}{16}\right)^{\text {th }}$ of its initial value?

A

40 minutes

B

60 minutes

C

80 minutes

D

20 minutes

Question 19: Palette 19/132

NEET 2023 MCQ

In hydrogen spectrum, the shortest wavelength in the Balmer series is $\lambda$. The shortest wavelength in the Bracket series is :

A

$4 \lambda$

B

$9 \lambda$

C

$16 \lambda$

D

$2 \lambda$

Question 20: Palette 20/132

NEET 2023 MCQ

The radius of inner most orbit of hydrogen atom is $5.3 \times 10^{-11} \mathrm{~m}$. What is the radius of third allowed orbit of hydrogen atom?

A

1.06 $\mathop A\limits^o $

B

1.59 $\mathop A\limits^o $

C

4.77 $\mathop A\limits^o $

D

0.53 $\mathop A\limits^o $

Question 21: Palette 21/132

NEET 2022 MCQ

Let R₁ be the radius of the second stationary orbit and R₂ be the radius of the fourth stationary orbit of an electron in Bohr's model. The ratio ${{{R_1}} \over {{R_2}}}$ is :

A

4

B

0.25

C

0.5

D

2

Question 22: Palette 22/132

NEET 2022 MCQ

Given below are two statements

Statement I : The law of radioactive decay states that the number of nuclei undergoing the decay per unit time is inversely proportional to the total number of nuclei in the sample.

Statement II : The half of a radionuclide is the sum of the life time of all nuclei, divided by the initial concentration of the nuclei at time t = 0.

In the light of the above statements, choose the most appropriate answer from the options given below :

A

Statement I is incorrect but statement II is correct

B

Both statement I and statement II are correct

C

Both statement I and statement II are incorrect

D

Statement I is correct but statement II is incorrect

Question 23: Palette 23/132

NEET 2022 MCQ

At any instant, two elements X₁ and X₂ have same number of radioactive atoms. If the decay constant of X₁ and X₂ are 10 $\lambda$ and $\lambda$ respectively, then the time when the ratio of their atoms becomes ${1 \over e}$ respectively will be :

A

${1 \over {5\lambda }}$

B

${1 \over {11\lambda }}$

C

${1 \over {9\lambda }}$

D

${1 \over {6\lambda }}$

Question 24: Palette 24/132

NEET 2022 MCQ

The ratio of Coulomb's electrostatic force to the gravitational force between an electron and a proton separated by some distance is 2.4 $\times$ 10³⁹. The ratio of the proportionality constant, $K = {1 \over {4\pi {\varepsilon _0}}}$ to the gravitational constant G is nearly (Given that the charge of the proton and electron each = 1.6 $\times$ 10^$-$19 C, the mass of the electron = 9.11 $\times$ 10^$-$31 kg, the mass of the proton = 1.67 $\times$ 10^$-$27 kg) :

A

10

B

10²⁰

C

10³⁰

D

10⁴⁰

Question 25: Palette 25/132

NEET 2022 MCQ

The graph which shows the variation of the de Broglie wavelength ($\lambda$) of a particle and its associated momentum (p) is

A

B

C

D

Question 26: Palette 26/132

NEET 2022 MCQ

In the given nuclear reaction, the element X is

${}_{11}^{22}Na \to X + {e^ + } + v$

A

${}_{11}^{23}Na$

B

${}_{10}^{23}Ne$

C

${}_{10}^{22}Ne$

D

${}_{12}^{22}Mg$

Question 27: Palette 27/132

NEET 2022 MCQ

Let T₁ and T₂ be the energy of an electron in the first and second excited states of hydrogen atoms, respectively. According to the Bohr's model of an atom, the ratio T₁ : T₂ is

A

1 : 4

B

4 : 1

C

4 : 9

D

9 : 4

Question 28: Palette 28/132

NEET 2022 MCQ

A nucleus of mass number 189 splits into two nuclei having mass number 125 and 64. The ratio of radius of two daughter nuclei respectively is

A

1 : 1

B

4 : 5

C

5 : 4

D

25 : 16

Question 29: Palette 29/132

NEET 2021 MCQ

A nucleus with mass number 240 breaks into two fragments each of mass number 120, the binding per nucleon of unfragmented nuclei is 7.6MeV while that of fragments is 8.5MeV. The total gain in the Binding Energy in the process is :

A

216MeV

B

0.9MeV

C

9.4MeV

D

804MeV

Question 30: Palette 30/132

NEET 2021 MCQ

The half life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be :

A

${2 \over {3\sqrt 2 }}$

B

${1 \over 2}$

C

${1 \over {2\sqrt 2 }}$

D

${2 \over 3}$

Question 31: Palette 31/132

NEET 2021 MCQ

A radioactive nucleus
$_Z^AX$ $\to$ ${}_{Z - 1}B$ $\to$ ${}_{Z - 3}C$ $\to$ ${}_{Z - 2}D$,
where Z is the atomic number of element X. The possible decay particles in the sequence are :

A

$\beta$^$-$, $\alpha$, $\beta$⁺

B

$\alpha$, $\beta$^$-$, $\beta$⁺

C

$\alpha$, $\beta$⁺, $\beta$^$-$

D

$\beta$⁺, $\alpha$, $\beta$^$-$

Question 32: Palette 32/132

NEET 2020 MCQ

When a uranium isotope $_{92}^{235}U$ is bombarded with a neutron, it generates $_{36}^{89}Kr$ three neutrons and :

A

${}_{40}^{91}Zr$

B

${}_{36}^{101}Kr$

C

${}_{36}^{103}Kr$

D

${}_{56}^{144}Ba$

Question 33: Palette 33/132

NEET 2020 MCQ

For which one of the following, Bohr model is not valid?

A

Singly ionised helium atom (He⁺)

B

Deuteron atom

C

Singly ionised neon atom (Ne⁺)

D

Hydrogen atom

Question 34: Palette 34/132

NEET 2020 MCQ

The energy equivalent of 0.5 g of a substance is :

A

$4.5 \times {10^{13}}J$

B

$1.5 \times {10^{13}}J$

C

$0.5 \times {10^{13}}J$

D

$4.5 \times {10^{16}}J$

Question 35: Palette 35/132

NEET 2019 MCQ

$\alpha $-particale consists of :

A

2 electrons, 2 protons and 2 neutrons

B

2 electrons and 4 protons only

C

2 protons only

D

2 protons and 2 neutrons only

Question 36: Palette 36/132

NEET 2019 MCQ

The total energy of an electron in an atom in an orbit is –3.4 eV. Its kinetic and potential energies are, respectively.

A

3.4 eV, – 6.8 eV

B

3.4 eV, 3.4 eV

C

– 3.4 eV, – 3.4 eV

D

– 3.4 eV, – 6.8 eV

Question 37: Palette 37/132

NEET 2018 MCQ

For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time taken (in minutes) for the disintegration of 450 nuclei is

A

20

B

10

C

30

D

15

Question 38: Palette 38/132

NEET 2018 MCQ

The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom, is

A

1 : 1

B

1 : -1

C

2 : -1

D

1 : -2

Question 39: Palette 39/132

NEET 2017 MCQ

The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is

A

1

B

4

C

0.5

D

2

Question 40: Palette 40/132

NEET 2017 MCQ

Radioactive material 'A' has decay constant '8 $\lambda $' and material 'B' has decay constant '$\lambda $'. Initially they have same number of nuclei. After what time, the ratio of number of nuclei of material 'B' to that 'A' will be e ?

A

${1 \over {7\lambda }}$

B

${1 \over {8\lambda }}$

C

${1 \over {9\lambda }}$

D

${1 \over {\lambda }}$

Question 41: Palette 41/132

NEET 2016 MCQ

The half-life of a radioactive substance is 30 minutes. The time (in minutes) taken between 40% decay and 85% decay of the same radioactive substance is

A

15

B

30

C

45

D

60

Question 42: Palette 42/132

NEET 2016 MCQ

If an electron in a hydrogen atom jumps from the 3^rd orbit to the 2^nd orbit, it emits a photon of wavelength $\lambda $. When it jumps from the 4^th orbit to the 3^rd orbit, the corresponding wavelength of the photon will be

A

${{16} \over {25}}\lambda $

B

${9 \over {16}}\lambda $

C

${{20} \over 7}\lambda $

D

${{20} \over {13}}\lambda $

Question 43: Palette 43/132

NEET 2016 MCQ

When an $\alpha $-particle of mass m moving with velocity v bombards on a heavy nucleus of charge Ze, its distance of closest approach from the nucleus depends on m as

A

${1 \over {{m^2}}}$

B

m

C

${1 \over m}$

D

${1 \over {\sqrt m }}$

Question 44: Palette 44/132

NEET 2016 MCQ

Given the value of Rydberg constant is 10⁷ m^$-$1, the wave number of the last line of the Balmer series in hydrogen spectrum will be

A

0.25 $ \times $ 10⁷ m^$-$1

B

2.5 $ \times $ 10⁷ m^$-$1

C

0.025 $ \times $ 10⁴ m^$-$1

D

0.5 $ \times $ 10⁷ m^$-$1

Question 45: Palette 45/132

NEET 2015 MCQ

In the spectrum of hydrogen, the ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series is

A

${{27} \over 5}$

B

${5 \over {27}}$

C

${4 \over 9}$

D

${9 \over 4}$

Question 46: Palette 46/132

NEET 2015 MCQ

A nucleus of uranium decays at rest into nuclei of thorium and helium. Then

A

The helium nucleus has more momentum than the thorium nucleus.

B

The helium nucleus has less kinetic energy than the thorium nucleus.

C

The helium nucleus has more kinetic energy than the thorium nucleus.

D

The helium nucleus has less momentum than the thorium nucleus.

Question 47: Palette 47/132

NEET 2015 MCQ

Consider 3^rd orbit of He⁺ (Helium), using non-relativistic approach, the speed of electron in this orbit will be [given K = 9 $ \times $ 10⁹ constant, Z = 2 and h (Planck's Constant) = 6.6 $ \times $ 10^$-$34 J s]

A

0.73 $ \times $ 10⁶ m/s

B

3.0 $ \times $ 10⁸ m/s

C

2.92 $ \times $ 10⁶ m/s

D

1.46 $ \times $ 10⁶ m/s

Question 48: Palette 48/132

NEET 2015 MCQ

If radius of the ${}_{13}^{27}$ Al nucleus is taken to be R_Al, then
the radius of ${}_{53}^{125}$Te nucleus is nearly

A

${3 \over 5}{R_{Al}}$

B

${\left( {{{13} \over {53}}} \right)^{1/3}}{R_{Al}}$

C

${\left( {{{53} \over {13}}} \right)^{1/3}}{R_{Al}}$

D

${5 \over 3}{R_{Al}}$

Question 49: Palette 49/132

NEET 2014 MCQ

Hydrogen atom in ground state is excited by a monochromatic radiation of $\lambda $ = 975 $\mathop A\limits^ \circ $. Number of spectral lines in the resulting spectrum emitted will be

A

3

B

2

C

6

D

0 10

Question 50: Palette 50/132

NEET 2014 MCQ

The binding energy per nucleon of and nuclei are 5.60 MeV and 7.06 MeV respectively. In the nuclear reaction

${}_3^7Li + {}_1^1H \to {}_2^4He + _2^4He + Q$

the value of energy Q released is

A

19.6 MeV

B

$-$ 2.4 MeV

C

8.4 MeV

D

17.3 MeV

Question 51: Palette 51/132

NEET 2014 MCQ

A radioactive X with a half life 1.4 $ \times $ 10⁹ years decays to Y which is stable. A sample of the rock from a cave was found to contain X and Y in the ratio 1 : 7. The age of the rock is

A

1.96 $ \times $ 10⁹ years

B

3.92 $ \times $ 10⁹ years

C

4.20 $ \times $ 10⁹ years

D

8.40 $ \times $ 10⁹ years

Question 52: Palette 52/132

NEET 2013 MCQ

$\alpha $-particles, $\beta $-particles and $\gamma $-rays are all having same energy. Their penetrating power in a given medium in increasing order will be

A

$\gamma $, $\alpha $, $\beta $

B

$\alpha $, $\beta $, $\gamma $

C

$\beta $, $\alpha $, $\gamma $

D

$\beta $, $\gamma $, $\alpha $

Question 53: Palette 53/132

NEET 2013 MCQ

An electron in hydrogen atom makes a transition n₁ $ \to $ n₂ where n₁ and n₂ are principal quantum numbers of the two states . Assuming Bohr's model to be valid, the time period of the electron in the initial state is eight times that in the final state. The possible values of n₁ and n₂ are

A

n₁ = 6 and n₂ = 2

B

n₁ = 8 and n₂ = 1

C

n₁ = 8 and n₂ = 2

D

n₁ = 4 and n₂ = 2

Question 54: Palette 54/132

NEET 2013 MCQ

How does the Binding Energy per nucleon vary with the increase in the number of nucleons ?

A

Decrease continuously with mass number.

B

First decreases and then increases with increase in mass number.

C

First increases and then decreases with increase in mass number.

D

increases continuously with mass number.

Question 55: Palette 55/132

NEET 2013 MCQ

Ratio of longest wave lengths corresponding to Lyman and Balmer series in hydrogen spectrum is

A

${7 \over {29}}$

B

${9 \over {31}}$

C

${5 \over {27}}$

D

${3 \over {23}}$

Question 56: Palette 56/132

NEET 2013 MCQ

A certain mass of Hydrogen is changed to Helium by the process of fusion. The mass defect in fusion reaction is 0.02866 u. The energy liberated per u is (given 1 u = 931 MeV)

A

6.675 MeV

B

13.35 MeV

C

2.67 MeV

D

26.7 MeV

Question 57: Palette 57/132

NEET 2013 MCQ

The half life of a radioactive isotope 'X' is 20 years. It decays to another element 'Y' which is stable. The two elements 'X' and 'Y' were found to be in the ratio 1 : 7 in a sample of a given rock. The age of the rock is estimated to be

A

80 years

B

100 years

C

40 years

D

60 years

Question 58: Palette 58/132

NEET 2012 MCQ

The half life of a radioactive nucleus is 50 days. The time invertal (t₂ $-$ t₁) between the time t₂ when ${2 \over 3}$ of it has decayed and the time t₁ when ${1 \over 3}$ of it had decayed is

A

30 days

B

50 days

C

60 days

D

15 days

Question 59: Palette 59/132

NEET 2012 MCQ

The transition from the state n = 3 to n = 1 in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from

A

2 $ \to $ 1

B

3 $ \to $ 2

C

4 $ \to $ 2

D

4 $ \to $ 3

Question 60: Palette 60/132

NEET 2012 MCQ

An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be

A

${{24hR} \over {25m}}$

B

${{25hR} \over {24m}}$

C

${{25m} \over {24hR}}$

D

${{24m} \over {25hR}}$

Question 61: Palette 61/132

NEET 2012 MCQ

Electron in hydrogen atom first jumps from third excited state to second excited state and then from second excited to the first excited state. The ratio of the wavelengths $\lambda $₁ : $\lambda $₂ emitted in the two cases is

A

${7 \over 5}$

B

${27 \over 20}$

C

${27 \over 5}$

D

${20 \over 7}$

Question 62: Palette 62/132

NEET 2012 MCQ

A mixture consists of two radioactive materials A₁ and A₂ with half lives of 20 s and 10 s respectively. Initially the mixture has 40 g of A₁ and 160 g of A₂. The amount of the two in the mixture will become equal after

A

60 s

B

80 s

C

20 s

D

40 s

Question 63: Palette 63/132

NEET 2012 MCQ

If the nuclear radius of ²⁷Al is 3.6 fermi, the approximate nuclear radius of ⁶⁴Cu in fermi is

A

2.4

B

1.2

C

4.8

D

3.6

Question 64: Palette 64/132

NEET 2011 MCQ

Out of the following which one is not a possible energy for a photon to be emitted by hydrogen atom according to Bohr's atomic model?

A

0.65 eV

B

1.9 eV

C

11.1 eV

D

13.6 eV

Question 65: Palette 65/132

NEET 2011 MCQ

Two radioactive nuclei P and Q, in a given sample decay into a stable nucleus R. At time t = 0. number of P species are 4 N₀ and that of Q are N₀. Half -life of P (for conversion to R) is 1 minute where as that of Q is 2 minutes. Initially there are no nuclei of R present in the sample. When number of nuclei of P and Q are equal, the number of nuclei of R present in the sample would be

A

2 N₀

B

3 N₀

C

${{9{N_0}} \over 2}$

D

${{5{N_0}} \over 2}$

Question 66: Palette 66/132

NEET 2011 MCQ

An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is 10 V, then the value of n is

A

2

B

3

C

4

D

5

Question 67: Palette 67/132

NEET 2011 MCQ

The half life of a radioactive isotope X is 50 years. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio of 1 : 15 in a sample of a given rock. The age of the rock was estimated to be

A

150 years

B

200 years

C

250 years

D

100 years

Question 68: Palette 68/132

NEET 2011 MCQ

The power obtained in a reactor using U²³⁵ disintegration is 1000 kW. The mass decay of U²³⁵ per hour is

A

10 microgram

B

20 microgram

C

40 microgram

D

1 microgram

Question 69: Palette 69/132

NEET 2011 MCQ

A radioactive nucleus of mass M emits a photon of frequency $v$ and the nucleus recoils. The recoil energy will be

A

Mc² $-$ h$v$

B

h²$\upsilon $²/2Mc²

C

zero

D

h$v$

Question 70: Palette 70/132

NEET 2011 MCQ

The wavelength of the first line of Lyman series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen like ion. The atomic number Z of hydrogen like ion is

A

3

B

4

C

1

D

2

Question 71: Palette 71/132

NEET 2011 MCQ

Fusion reaction takes place at high temperature because

A

nuclei break up at high temperature

B

atoms get ionised at high temperature

C

kinetic energy is high enough to overcome the coulomb repulsion between nuclei

D

molecules break up at high temperature

Question 72: Palette 72/132

NEET 2011 MCQ

A nucleus ${}_n^mX$ emits one $\alpha $ particle and two $\beta $ particles. The resulting nucleus is

A

${}_{n - 4}^{m - 6}Z$

B

${}_n^{m - 6}Z$

C

${}_n^{m - 4}X$

D

${}_{n - 2}^{m - 4}Y$

Question 73: Palette 73/132

NEET 2010 MCQ

The decay constant of a radio isotope is $\lambda $. If A₁ and A₂ are its activities at times t₁ and t₂ respectively, the number of nuclei which have decayed during the time (t₁ $-$ t₂)

A

A₁t₁ $-$ A₂t₂

B

A₁ $-$ A₂

C

(A₁ $-$ A₂)/$\lambda $

D

$\lambda ({A_1} - {A_2})$

Question 74: Palette 74/132

NEET 2010 MCQ

The binding energy per nucleon in deuterium and helium nuclei are 1.1 MeV and 7.0 MeV, respectively. When two deuterium nuclei fuse to form a helium nucleus the energy released in the fusion is

A

23.6 MeV

B

2.2 MeV

C

28.0 MeV

D

30.2 MeV

Question 75: Palette 75/132

NEET 2010 MCQ

The activity of a radioactive sample is measured as N₀ counts per minute at t = 0 and N₀/e counts per minute at t = 5 minutes. The time (in minutes) at which the activity reduces to half its value is

A

${\log _e}{2 \over 5}$

B

${5 \over {{{\log }_e}2}}$

C

5log₁₀2

D

5log_e 2

Question 76: Palette 76/132

NEET 2010 MCQ

An alpha nucleus of energy ${1 \over 2}$ mv² bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to

A

${1 \over {Ze}}$

B

v²

C

${1 \over m}$

D

${1 \over {{v_4}}}$

Question 77: Palette 77/132

NEET 2010 MCQ

The mass of a ${}_3^7Li$ Li nucleus is 0.042 u less than the sum of the masses of all its nucleons. The binding energy per nucleon of ${}_3^7Li$ nucleus is nearly

A

46 MeV

B

5.6 MeV

C

3.9 MeV

D

23 MeV

Question 78: Palette 78/132

NEET 2010 MCQ

The energy of a hydrogen atom in the ground state is $-$ 13.6 eV. The energy of a He⁺ ion in the first excited state will be

A

$-$ 13.6 eV

B

$-$ 27.2 eV

C

$-$ 54.4 eV

D

$-$ 6.8 eV

Question 79: Palette 79/132

NEET 2010 MCQ

The energy of a hydrogen atom in the ground state is $-$ 13.6 eV. The energy of a He⁺ ion in the first excited state will be

A

$-$ 13.6 eV

B

$-$ 27.2 eV

C

$-$ 54.4 eV

D

$-$ 6.8 eV

Question 80: Palette 80/132

NEET 2009 MCQ

In a Rutherford scattering experiment when a projectile of charge z₁ and mass M₁ approaches a target nucleus of charge z₂ and mass M₂, the distance of closest approach is r₀. The energy of the projectile is

A

directly proportional to z₁z₂

B

inversely proportional to z₁

C

directly proportional to mass M₁

D

directly proportional to M₁ $ \times $ M₂

Question 81: Palette 81/132

NEET 2009 MCQ

The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an

A

isomer of parent

B

isotone of parent

C

isotope of parent

D

isobar of parent

Question 82: Palette 82/132

NEET 2009 MCQ

In the nuclear decay given below

${}_Z^AX \to {}_{Z + 1}^AY \to {}_{Z - 1}^{A - 4}B{}^ * \to {}_{Z - 1}^{A - 4}B,$

the particles emitted in the sequence are

A

$\gamma $, $\beta $, $\alpha $

B

$\beta $, $\gamma $, $\alpha $

C

$\alpha $, $\beta $, $\gamma $

D

$\beta $, $\alpha $, $\gamma $

Question 83: Palette 83/132

NEET 2009 MCQ

The ionization energy of the electron in the hydrogen atom in its ground state is 13.6 eV. The atoms are excited to higher energy levels to emit radiations of 6 wavelengths, Maximum wavelength of emitted radiation corresponds to the transition between

A

n = 3 to n = 1 states

B

n = 2 to n = 1 states

C

n = 4 to n = 3 states

D

n = 3 to n = 2 states

Question 84: Palette 84/132

NEET 2008 MCQ

Two radioactive materials X₁ and X₂ have decay constants $5\lambda $ and $\lambda $ respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of X₁ to that X₂ will be 1/e after a time

A

1/4$\lambda $

B

e/$\lambda $

C

$\lambda $

D

${1 \over 2}\lambda $

Question 85: Palette 85/132

NEET 2008 MCQ

The ground state energy of hydrogen atom is $-$ 13.6 eV. When its electron is in the first excited state, its excitation energy is

A

10.2 eV

B

0

C

3.4 eV

D

6.8 eV

Question 86: Palette 86/132

NEET 2008 MCQ

Two nuclei have their mass numbers in the ratio of 1 : 3. The ratio of their nuclear densities would be

A

${\left( 3 \right)^{1/3}}:1$

B

1 : 1

C

1 : 3

D

3 : 1

Question 87: Palette 87/132

NEET 2008 MCQ

If M(A; Z), M_p and M_n denote the masses of the nucleus ${}_Z^AX,$ proton and neutron respectively in units of u (1 u = 931.5 MeV/c²) and BE represents its bonding energy in MeV, then

A

M(A, Z) = ZM_p + (A $-$ Z)M_n $-$ BE

B

M(A, Z) = ZM_p + (A $-$ Z)M_n + BE/c²

C

M(A, Z) = ZM_p + (A $-$ Z)M_n $-$ BE/c²

D

M(A, Z) = ZM_p + (A $-$ Z)M_n + BE

Question 88: Palette 88/132

NEET 2007 MCQ

In a radioactive decay process, the negatively charged emitted $\beta $-particles are

A

the electrons produced as a result of the decay of neutrons inside the nucleus

B

the electrons produced as a result of collisions between atoms

C

the electrons orbitting around the nucleus

D

the electrons present inside the nucleus

Question 89: Palette 89/132

NEET 2007 MCQ

If the nucleus ${}_{13}^{27}Al$ has a nuclear radius of about 3.6 fm, them ${}_{32}^{125}Te$ would have its radius approximately as

A

9.6 fm

B

12.0 fm

C

4.8 fm

D

6.0 fm

Question 90: Palette 90/132

NEET 2007 MCQ

In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential $V$ and then made to describe semicircular paths of radius R using a magnetic field B. If V and B are kept constant, the ratio $\left( {{{ch\arg e\,\,on\,\,\,the\,\,ion\,\,} \over {mass\,\,of\,\,the\,\,ion}}} \right)$ will be proportional to

A

1/R²

B

R²

C

R

D

1/R

Question 91: Palette 91/132

NEET 2007 MCQ

A nucleus ${}_Z^AX$ has mass represented by M(A, Z). If M_p and M_n denote the mass of proton and neutron respectively and B.E. the binding energy in MeV, then

A

B.E. = [ZM_p + (A $-$ Z)M_n $-$ M(A, Z)]c²

B

B.E. = [ZM_p + AM_p $-$ M(A, Z)]c²

C

B.E. = M(A, Z) $-$ ZM_p $-$ (A $-$ Z)M_n

D

B.E. = [M(A, Z) $-$ ZM_p $-$ (A $-$ Z)M_n]c²

Question 92: Palette 92/132

NEET 2007 MCQ

Two radioactive substances A and B have decay constants 5$\lambda $ and $\lambda $ respectively. At t = 0 they have the same number of nuclei. The ratio of number of nuclei of A to those of B will be (1/e)² after a time interval

A

$4\lambda $

B

$2\lambda $

C

1/$2\lambda $

D

1/$4\lambda $

Question 93: Palette 93/132

NEET 2007 MCQ

The total energy of electron in the ground state of hydrogen atom is $-$ 13.6 eV. The kinetic energy of an electron in the first excited state is

A

6.8 eV

B

13.6 eV

C

1.7 eV

D

3.4 eV.

Question 94: Palette 94/132

NEET 2006 MCQ

The radius of germanium (Ge) nuclide is measured to be twice the radius of ${}_4^9$Be. The number of nucleons in Ge are

A

72

B

73

C

74

D

75

Question 95: Palette 95/132

NEET 2006 MCQ

In a radioactive material the activity at time t₁ is R₁ and at a later time t₂, it is R₂. If the decay constant of the material is $\lambda $, then

A

R₁ = R₂

B

R₁ = R₂e^{$-$$\lambda $(t₁$-$t₂)}

C

R₁ = R₂e^{$\lambda $(t₁$-$t₂)}

D

R₁ = R₂(t₂/t₁).

Question 96: Palette 96/132

NEET 2006 MCQ

Ionization potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. According to Bohr's theory, the spectral lines emited by hydrogen will be

A

one

B

two

C

three

D

four

Question 97: Palette 97/132

NEET 2006 MCQ

The binding energy of deuteron is 2.2 MeV and that of ${}_2^4$He is 28 MeV. If two deuterons are fused to form one ${}_2^4$He then the energy released is

A

30.2 MeV

B

25.8 MeV

C

23.6 MeV

D

19.2 MeV

Question 98: Palette 98/132

NEET 2005 MCQ

Which one of the following pairs of nuclei are isotones ?

A

₃₄Se⁷⁴,  ₃₁Ga⁷¹

B

₃₈Sr⁸⁴,  ₃₈Sr⁸⁶

C

₄₂Mo⁹²,   ₄₀Zr⁹²

D

₂₀Ca⁴⁰,  ₁₆S³²

Question 99: Palette 99/132

NEET 2005 MCQ

In any fission process the ratio

mass of fission products

mass of parent nucleus

is

A

equal to 1

B

greater than 1

C

less than 1

D

depends on the mass of the parent nucleus.

Question 100: Palette 100/132

NEET 2005 MCQ

In the reaction ${}_1^2$H + ${}_1^3$H $ \to $ ${}_2^4$He + ${}_0^1$n, if the binding
energies of ${}_1^2$ H, ${}_1^3$H and ${}_2^4$He are respectively a, b and c (in MeV),
then the energy (in MeV) released in this reaction is

A

a + b + c

B

a + b $-$ c

C

c $-$ a $-$ b

D

c + a $-$ b

Question 101: Palette 101/132

NEET 2005 MCQ

Energy levels A, B and C of a certain atom corresponding to increasing values of energy i.e. E_A < E_B < E_C. If $\lambda $₁, $\lambda $₂ and $\lambda $₃ are wavelengths of radioations corresponding to transitions C to B, B to A and C to A respectively, which of the following relations is correct?

A

${\lambda _3} = {\lambda _1} + {\lambda _2}$

B

${\lambda _3} = {{{\lambda _1}{\lambda _2}} \over {{\lambda _1} + {\lambda _2}}}$

C

${\lambda _1} + {\lambda _2} + {\lambda _3} = 0$

D

${\lambda _3}^2 = {\lambda _1}^2 + {\lambda _2}^2$

Question 102: Palette 102/132

NEET 2005 MCQ

Fission of nuclei is possible because the binding energy per nucleon in them

A

increases with mass number at low mass numbers

B

decreases with mass number at low mass numbers

C

increases with mass number at high mass numbers

D

decreases with mass number at high mass numbers.

Question 103: Palette 103/132

NEET 2005 MCQ

The total energy of an electron in the first excited state of hydrogen atom is about $-$ 3.4 eV. Its kinetic energy in this state is

A

3.4 eV

B

6.8 eV

C

$-$ 3.4 eV

D

$-$ 6.8 eV

Question 104: Palette 104/132

NEET 2004 MCQ

The Bohr model of atoms

A

Assumes that the angular momentum of electrons is quantized.

B

Uses Einstein's photoelectric equation.

C

Predicts continuous emission spectra fror atoms.

D

Predicts the same emission spectra for all types of atoms.

Question 105: Palette 105/132

NEET 2004 MCQ

If in a nuclear fusion process the masses of the fusing nuclei be m₁ and m₂ and the mass of the resultant nucleus be m₃, then

A

m₃ = m₁ + m₂

B

m₃ = $\left| {{m_1} - {m_2}} \right|$

C

m₃ < (m₁ + m₂)

D

m₃ > (m₁ + m₂)

Question 106: Palette 106/132

NEET 2004 MCQ

A nucleus represented by the symbol ${}_Z^AX$ has

A

Z neutrons and A $-$ Z protons

B

Z protons and A $-$ Z neutrons

C

Z protons and A neutrons

D

A protons and Z $-$ A neutrons

Question 107: Palette 107/132

NEET 2004 MCQ

If M(A; Z), M_p and M_n denote the masses of the nucleus ${}_Z^AX,$ proton and neutron respectively in units of u (1 u = 931.5 MeV/c²) and BE represents its bonding energy in MeV, then

A

M(A, Z) = ZM_p + (A $-$ Z)M_n $-$ BE

B

M(A, Z) = ZM_p + (A $-$ Z)M_n + BE/c²

C

M(A, Z) = ZM_p + (A $-$ Z)M_n $-$ BE/c²

D

M(A, Z) = ZM_p + (A $-$ Z)M_n + BE

Question 108: Palette 108/132

NEET 2004 MCQ

The half life of radian is about 1600 years. Of 100 g of radium existing now, 25 g will remain unchanged after

A

4800 years

B

6400 years

C

2400 years

D

3200 years

Question 109: Palette 109/132

NEET 2003 MCQ

In which of the following systems will the radius of the first orbit (n = 1) be minimum ?

A

doubly ionized lithium

B

singly ionized helium

C

deuterium atom

D

hydrogen atom

Question 110: Palette 110/132

NEET 2003 MCQ

The mass of proton is 1.0073 u and that of neutron is 1.0087 u (u = atomic mass unit). The binding energy of ${}_2^4$ He is
(Given helium nucleus mass $ \approx $ 4.0015 u.)

A

0.0305 J

B

0.0305 erg

C

28.4 MeV

D

0.061 u

Question 111: Palette 111/132

NEET 2003 MCQ

The mass number of a nucleus is

A

always less than its atomic number

B

always more than its atomic number

C

sometimes equal to its atomic number

D

sometimes less than and sometimes more than its atomic number

Question 112: Palette 112/132

NEET 2003 MCQ

An electron is moving round the nucleus of a hydrogen atom in a circular orbit of radius r. The Coulomb force $\overrightarrow F $ between the two is

A

$K{{{e^2}} \over {{r^2}}}\widehat r$

B

$ - K{{{e^2}} \over {{r^3}}}\widehat r$

C

$K{{{e^2}} \over {{r^3}}}\widehat r$

D

$ - K{{{e^2}} \over {{r^2}}}\widehat r$

Question 113: Palette 113/132

NEET 2003 MCQ

Solar energy is mainly caused due to

A

burning of hydrogen in the oxygen

B

fission of uranium present in the Sun

C

fusion of protons during synthesis of heavier elements

D

gravitational contraction

Question 114: Palette 114/132

NEET 2003 MCQ

A sample of radioactive element has a mass of 10 g at an instant t = 0. The approximate mass of this element in the sample after two mean lives is

A

1.35 g

B

2.50 g

C

3.70 g

D

6.30 g

Question 115: Palette 115/132

NEET 2003 MCQ

A nuclear reaction given by

_ZX^A $ \to $ _z+1Y^A + _$-$1e⁰ + $\overline v $ represents

A

$\beta $-decay

B

$\gamma $-decay

C

fusion

D

fission

Question 116: Palette 116/132

NEET 2003 MCQ

The volume occupied by an atom is greater than the volume of the nucleus by a factor of about

A

10¹

B

10⁵

C

10¹⁰

D

10¹⁵

Question 117: Palette 117/132

NEET 2002 MCQ

A sample of radioactive element containing 4 $ \times $ 10¹⁶ active nuclei. Half life of element is 10 days, then number of decayed nuclei after 30 days

A

0.5 $ \times $ 10¹⁶

B

2 $ \times $ 10¹⁶

C

3.5 $ \times $ 10¹⁶

D

1 $ \times $ 10¹⁶

Question 118: Palette 118/132

NEET 2002 MCQ

A deutron is bombarded on ₈O¹⁶ nucleus then $\alpha $-particle is emitted. The product nucleus is

A

₇N¹³

B

₅B¹⁰

C

₄Be⁹

D

₇N¹⁴

Question 119: Palette 119/132

NEET 2002 MCQ

Which of the following are suitable for the fusion process ?

A

light nuclei

B

heavy nuclei

C

element lying in the middle of the periodic table

D

middle elements, which are lying on binding energy curve.

Question 120: Palette 120/132

NEET 2001 MCQ

Which rays contain (positive) charged particles ?

A

$\alpha $-rays

B

$\beta $-rays

C

$\gamma $-rays

D

X-rays

Question 121: Palette 121/132

NEET 2001 MCQ

M_n and M_p represent the mass of neutron and proton respectively. An element having mass M has N neutrons and Z protons, then the correct relation will be

A

M < {N $ \cdot $ M_n + Z $ \cdot $ M_p}

B

M > {N $ \cdot $ M_n + Z $ \cdot $ M_p}

C

M = {N $ \cdot $ M_n + Z $ \cdot $ M_p}

D

M = N {M_n + M_p}

Question 122: Palette 122/132

NEET 2001 MCQ

X(n, $\alpha $) ${}_3^7$Li, then X will be

A

${}_5^{10}$ B

B

${}_5^9$ B

C

${}_5^{11}$ Be

D

${}_2^4$ He.

Question 123: Palette 123/132

NEET 2001 MCQ

Energy released in nuclear fission is due to

A

some mass is converted into energy

B

total binding energy of fragments is more than the binding energy of parantal element

C

total binding energy of fragments is less than the binding energy of parental element

D

total binding energy of fragments is equal to the binding energy of parental element.

Question 124: Palette 124/132

NEET 2001 MCQ

The energy of hydrogen atom in n^th orbit is E_n then the energy in n^th orbit of singly ionised helium atom will be

A

4E_n

B

E_n/4

C

2E_n

D

E_n/2

Question 125: Palette 125/132

NEET 2001 MCQ

The interplanar distance in a crystal is 2.8 $ \times $ 10^$-$8 m. The value of maximum wavelength which can be diffracted

A

2.8 $ \times $ 10^$-$8 m

B

5.6 $ \times $ 10^$-$8 m

C

1.4 $ \times $ 10^$-$8 m

D

7.6 $ \times $ 10^$-$8 m

Question 126: Palette 126/132

NEET 2001 MCQ

Half life of a radioactive element is 12.5 hour and its quantity is 256 g. After how much time its quantity will remain 1 g?

A

50 hrs

B

100 hrs

C

150 hrs

D

200 hrs

Question 127: Palette 127/132

NEET 2000 MCQ

Maximum frequency of emission is obtained for the transition

A

n = 2 to n = 1

B

n = 6 to n = 2

C

n = 1 to n = 2

D

n = 2 to n = 6.

Question 128: Palette 128/132

NEET 2000 MCQ

The relation between $\lambda $ and T_1/2 as (T_1/2 $ \to $ half life)

A

T_1/2 = ${{\ln 2} \over \lambda }$

B

T_1/2 ln2 = $\lambda $

C

T_1/2 = ${1 \over \lambda }$

D

($\lambda $ + T_1/2) = ln2

Question 129: Palette 129/132

NEET 2000 MCQ

Nuclear fission is best explained by

A

liquid droplet theory

B

Yukawa $\pi $-meson theory

C

independent particle model of the nucleus

D

proton-proton cycle.

Question 130: Palette 130/132

NEET 2000 MCQ

The life span of atomic hydrogen is

A

fraction of one second

B

one year

C

one hour

D

one day

Question 131: Palette 131/132

NEET 2000 MCQ

For the given reaction, the particle X is
$_6{C^{11}} \to {}_5{B^{11}} + {\beta ^ + } + X$

A

neutron

B

anti neutrino

C

neutrino

D

proton

Question 132: Palette 132/132

NEET 2000 MCQ

When an electron does transition from n = 4 to n = 2, then emitted line spectrum will be

A

first line of Lyman series

B

second line of Balmer series

C

first line of Balmer series

D

second line of Paschen series.