iCON Education - Modern Physics

Q1 DPT Photon MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

Power of a radiator is 100 watt and its $\lambda$ is 400 nm. Calculate No. of photon emitted in 10 hrs.

A.

$7.2 \times 10^{24}$

B.

$2.0 \times 10^{20}$

C.

$3.6 \times 10^{22}$

D.

$5.0 \times 10^{24}$

Q2 DPT Photon MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

A source $S_{1}$ is producing $10^{15}$ photon/s of wavelength 5000 Å. Another source $S_{2}$ is producing $1.02 \times 10^{15}$ photon/s of wavelength 5100 Å. Calculate ratio of power of $S_{2}$ to power of $S_{1}$.

A.

$1 : 2$

B.

$1 : 1$

C.

$2 : 1$

D.

$1.02 : 1$

Q3 DPT Photon MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

In a photo-electric experiment frequency of incident light is doubled and its intensity is tripled. How much time the photon current is obtained?

A.

$3/2$ times

B.

$2/3$ times

C.

$3$ times

D.

$6$ times

Q4 DPT Photon MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

The energy flux of sunlight reaching the Earth's surface is $1.388 \times 10^{3} \text{ W m}^{-2}$. How many photons (nearly) per square meter are incident on the earth per second? Assume that the photons in the sunlight have an average wavelength of $1550 \text{ nm}$.

A.

$1.08 \times 10^{22}$

B.

$3.83 \times 10^{21}$

C.

$2.50 \times 10^{20}$

D.

$1.38 \times 10^{23}$

Q5 DPT Photon MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

The power of a bulb is 60 milliwatt and the wavelength of light is 6000 Å. Calculate the number of photons/second emitted by the bulb?

A.

$1.8 \times 10^{17} \text{ photon/sec}$

B.

$3.2 \times 10^{18} \text{ photon/sec}$

C.

$5.4 \times 10^{16} \text{ photon/sec}$

D.

$2.5 \times 10^{17} \text{ photon/sec}$

Q6 DPT Photon MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

The energy flux of sunlight reaching on the Earth's surface is $1.388 \times 10^{3} \text{ W/m}^{2}$. How many photons (nearly) per square metre are incident on the Earth per second? Assume that the photons in the sunlight have an average length of 550 nm.

A.

$1.50 \times 10^{20} \text{ photon/m}^{2}\text{s}$

B.

$3.83 \times 10^{21} \text{ photon/m}^{2}\text{s}$

C.

$7.20 \times 10^{22} \text{ photon/m}^{2}\text{s}$

D.

$4.12 \times 10^{19} \text{ photon/m}^{2}\text{s}$

Correct Answer: B

Explanation:

$\text{Intensity, } I = \frac{\text{Power emitted}}{\text{Area}} = \frac{P}{A} = 1.388 \times 10^{3} \text{ W/m}^{2}$
$\text{Also, Energy of a photon, } E = \frac{hc}{\lambda} = \frac{6.63 \times 10^{-34} \times 3 \times 10^{8}}{550 \times 10^{-9}} = 3.616 \times 10^{-19} \text{ J}$
$\text{Let } n \text{ be the total number of photon/area then, } n = \frac{P/A}{E} = \frac{I}{E} = \frac{1.388 \times 10^{3}}{3.616 \times 10^{-19}} = 3.83 \times 10^{21} \text{ photon/m}^{2}\text{s}$

Q7 DPT Photon MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

A beam of electromagnetic wave of power 10 watt is incident normally on a surface, which absorb 40% power and remaining power is reflected. Calculate force exerted on a surface.

A.

$5.33 \times 10^{-8} \text{ N}$

B.

$3.33 \times 10^{-8} \text{ N}$

C.

$1.60 \times 10^{-7} \text{ N}$

D.

$2.67 \times 10^{-8} \text{ N}$

Q8 DPT Photon MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

A 100 W sodium lamp radiates energy uniformly in all directions. The lamp is located at the centre of a large sphere that absorbs all the sodium light, which is incident on it. The wavelength of the sodium light is 589 nm. (a) What is the energy per photon associated with the sodium light? (b) At what rate are the photons delivered to the sphere?

A.

$E = 3.38 \times 10^{-19} \text{ J}, n = 2.96 \times 10^{20} \text{ photons/s}$

B.

$E = 2.11 \times 10^{-19} \text{ J}, n = 5.00 \times 10^{20} \text{ photons/s}$

C.

$E = 4.12 \times 10^{-19} \text{ J}, n = 1.50 \times 10^{20} \text{ photons/s}$

D.

$E = 1.80 \times 10^{-19} \text{ J}, n = 3.20 \times 10^{20} \text{ photons/s}$

Q9 DPT Photon MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

How many photons of wavelength $\lambda = 6600 \text{ nm}$ must strike a totally reflecting screen per second at normal incidence so as to exert a force of 1 N?

A.

$5 \times 10^{27} \text{ photons/s}$

B.

$2.5 \times 10^{27} \text{ photons/s}$

C.

$1 \times 10^{28} \text{ photons/s}$

D.

$3.3 \times 10^{26} \text{ photons/s}$

Correct Answer: A

Explanation:

Momentum of the incident photon, $p = \frac{h}{\lambda}$
Change in momentum $=\Delta p = \frac{2h}{\lambda}$
Momentum after reflection $=-\frac{h}{\lambda}$
If n is the number of photons falling per second on the screen, then force
$F = \frac{\Delta p}{\Delta t} = \frac{2nh}{\lambda} \Rightarrow n = \frac{F\lambda}{2h} = \frac{1 \times 6600 \times 10^{-9}}{2 \times 6.6 \times 10^{-34}} = 5 \times 10^{27} \text{ photons s}^{-1}$

Q10 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

The threshold wavelength of a metal is 400 nm. Photo electrons have kinetic energy maximum 1.5 eV. Find the wavelength of incident photon.

A.

2696 Å

B.

4000 Å

C.

3100 Å

D.

1850 Å

Correct Answer: A

Explanation:

$\lambda_{0} = 400 \text{ nm} = 4000 \text{ Å}$
$\text{K.E.}_{\text{max.}} = \frac{12400 \text{ eVÅ}}{\lambda} - \frac{12400 \text{ eVÅ}}{\lambda_{0}}$
$1.5 \text{ eV} = \frac{12400 \text{ eVÅ}}{\lambda} - \frac{12400 \text{ eV}}{4000} \implies 1.5 \text{ eV} = \frac{12400 \text{ eVÅ}}{\lambda} - 3.1 \text{ eV}$
$(1.5 + 3.1) \text{ eV} = \frac{12400 \text{ eVÅ}}{\lambda} \implies \lambda = \frac{12400 \text{ Å}}{4.6} \implies \lambda = 2696 \text{ Å}$

Q11 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

The work function of a metal is 2.3 eV and the wavelength of incident photon is $4.8 \times 10^{-7}\text{ m}$. Find maximum kinetic energy of photo electrons.

A.

0.28 eV

B.

1.50 eV

C.

2.30 eV

D.

0.58 eV

Q12 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

Light quanta with an energy 4.9 eV eject photoelectrons from metal with work function 4.5 eV. Find the maximum impulse transmitted to the surface of the metal when each electron flies out.

A.

$3.43 \times 10^{-25} \text{ kg m/s}$

B.

$1.60 \times 10^{-25} \text{ kg m/s}$

C.

$5.20 \times 10^{-25} \text{ kg m/s}$

D.

$2.80 \times 10^{-24} \text{ kg m/s}$

Correct Answer: A

Explanation:

According to Einstein's photoelectric equation
$K_{\text{max}} = \frac{1}{2}mv_{\text{max}}^{2} = h\nu - \phi_{0} = 4.9 - 4.5 = 0.4 \text{ eV}$
Change of momentum $(p_{2} - p_{1}) = \text{impulse} \therefore \text{impulse} = mv - \left(-\frac{E}{c}\right) = mv + E/c$
Maximum impulse $= \sqrt{2mK_{\text{max}}} + \frac{E}{c} = \frac{4.9 \times 10^{-19} \times 1.6}{3 \times 10^{8}} + \sqrt{2 \times 0.4 \times 1.6 \times 10^{-19} \times 9.1 \times 10^{-31}} = 3.43 \times 10^{-25} \text{ kg m/s}$

Q13 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

The work function of a metal is 4 eV if 5000 Å wavelength of light is incident on the metal. Is there any photo electric effect?

A.

Yes, with maximum kinetic energy 1.52 eV

B.

No, because $E < \phi$

C.

Yes, with maximum kinetic energy 2.48 eV

D.

Data insufficient

Q14 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

In a photo cell 4 unit photo electric current is flowing, the distance between source and cathode is 4 unit. Now distance between source and cathode becomes 1 unit. What will be photo electric current now?

A.

16 units

B.

32 units

C.

64 units

D.

4 units

Q15 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

The wavelength of photons in two cases are 4000 Å and 3600 Å respectively what is difference in stopping potential for these two?

A.

0.34 V

B.

0.68 V

C.

1.25 V

D.

0.15 V

Q16 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

Threshold frequency of a surface is $\nu_{0}$. It is illuminated by $3\nu_{0}$ frequency, then maximum speed of photo electrons is $V \text{ m/sec}$. What will be maximum speed if incident frequency is $9\nu_{0}$?

A.

$2V$

B.

$V/2$

C.

$4V$

D.

$3V$

Q17 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

When incident wavelength is $\lambda$, stopping potential is $3V_{0}$. If incident wavelength is $2\lambda$ then stopping potential is $V_{0}$. Find out threshold wavelength in terms of $\lambda$.

A.

$2\lambda$

B.

$4\lambda$

C.

$3\lambda$

D.

$6\lambda$

Correct Answer: B

Explanation:

$e(3V_{0}) = \frac{hc}{\lambda} - \frac{hc}{\lambda_{0}}$
$e V_{0} = \frac{hc}{2\lambda} - \frac{hc}{\lambda_{0}}$
$3\left(\frac{hc}{2\lambda} - \frac{hc}{\lambda_{0}}\right) = \frac{hc}{\lambda} - \frac{hc}{\lambda_{0}}$
$\frac{3hc}{2\lambda} - \frac{3hc}{\lambda_{0}} = \frac{hc}{\lambda} - \frac{hc}{\lambda_{0}}$
$\frac{hc}{2\lambda} = \frac{2hc}{\lambda_{0}} \implies \lambda_{0} = 4\lambda$

Q18 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

A light beam of power 1.5 mW and 400 nm wavelength incident on a cathode. If quantum efficiency is 0.1% then, find out obtained photo current and number of photoelectron per second.

A.

$i = 0.24 \ \mu\text{A}, n_{e} = 1.5 \times 10^{12} \text{ s}^{-1}$

B.

$i = 0.96 \ \mu\text{A}, n_{e} = 6.0 \times 10^{12} \text{ s}^{-1}$

C.

$i = 0.48 \ \mu\text{A}, n_{e} = 3.0 \times 10^{12} \text{ s}^{-1}$

D.

$i = 1.20 \ \mu\text{A}, n_{e} = 4.5 \times 10^{12} \text{ s}^{-1}$

Correct Answer: C

Explanation:

$n_{\text{ph}} = (5 \times 10^{24} \text{ J}^{-1}\text{m}^{-1}) P \lambda = 5 \times 10^{24} \times 1.5 \times 10^{-3} \times 400 \times 10^{-9} = 3 \times 10^{15} \text{ photons/sec}$
$n_{e} = \frac{0.1}{100} \times n_{\text{ph}} = 10^{-3} \times 3 \times 10^{15} = 3 \times 10^{12} \text{ photoelectrons/sec}$
$i = n_{e} e = 3 \times 10^{12} \times 1.6 \times 10^{-19} \text{ A} = 4.8 \times 10^{-7} \text{ A} = 0.48 \ \mu\text{A}$

Q19 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

A metallic surface of work function $h\nu$ is illuminated by a radiation beam of frequency $5\nu$. Stopping potential observed is $X$. What will be stopping potential if the surface is illuminated by radiations of $7\nu$ frequency?

A.

$1.5 X$

B.

$2.5 X$

C.

$3.0 X$

D.

$1.2 X$

Q20 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

The kinetic energy of the fastest moving photo electron from a metal of work function 2.8 eV is 2 eV. If the frequency of light is doubled, then find the maximum kinetic energy of photo electron.

A.

4.0 eV

B.

6.8 eV

C.

5.6 eV

D.

9.6 eV

Q21 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

A monochromatic light incident on metal 'A' having threshold frequency $\nu_{0}$. It emits photo electrons of maximum kinetic energy $K$. Now incident frequency is made three times and fall on a metal 'B' having threshold frequency $2\nu_{0}$. What will maximum kinetic energy of photo electrons emitted by metal 'B'?

A.

$3K + h\nu_{0}$

B.

$2K + h\nu_{0}$

C.

$3K - h\nu_{0}$

D.

$K + 2h\nu_{0}$

Q22 DPT Photo Electric Effect MCQ

iCON Education HYD, 79930 92826, 73309 72826 08 Sep 2026

Concept:

If light of wavelength 4000 Å falls on a metal which has a stopping potential 1.4 volt against photoelectric emission then what is the work function of the metal. [Take $h = 6.6 \times 10^{-34} \text{ Js}$ and $c = 3 \times 10^{8} \text{ ms}^{-1}$]

A.

1.7 eV

B.

3.1 eV

C.

1.4 eV

D.

2.5 eV

Q23 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

With what potential an electron should be accelerated so that its de-Broglie wavelength becomes $10 \text{ Å}$?

A.

$1.0 \text{ volt}$

B.

$2.0 \text{ volt}$

C.

$1.5 \text{ volt}$

D.

$15 \text{ volt}$

Q24 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

Find the ratio of de-Broglie wavelengths for a proton and an alpha particle, if both have same speed.

A.

$4:1$

B.

$1:4$

C.

$2:1$

D.

$1:2$

Q25 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

Find the ratio of de-Broglie wavelength for a proton and a deutron, if both have same kinetic energy.

A.

$1:\sqrt{2}$

B.

$2:1$

C.

$1:2$

D.

$\sqrt{2}:1$

Q26 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

Compute the typical de-Broglie wavelength of an electron in a metal at 27°C and compare it with the mean separation between two electrons in a metal, which is given to be about $2 \times 10^{-10} \text{ m}$.

A.

$6.2 \times 10^{-10} \text{ m}$

B.

$2.0 \times 10^{-10} \text{ m}$

C.

$6.2 \times 10^{-9} \text{ m}$

D.

$3.1 \times 10^{-9} \text{ m}$

Correct Answer: C

Explanation:

$\lambda = \frac{h}{\sqrt{3mkT}}$
$\lambda = \frac{6.6 \times 10^{-34}}{\sqrt{3(9.1 \times 10^{-31})(1.38 \times 10^{-23})(273 + 27)}}$
$\lambda = 6.2 \times 10^{-9} \text{ m}$
As mean separation between two electrons $r = 2 \times 10^{-10} \text{ m}$
$\frac{r}{\lambda} = \frac{2 \times 10^{-10}}{6.2 \times 10^{-9}} \approx 0.03$

Q27 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

Calculate de-Broglie wavelength of an electron revolving in first excited state in hydrogen atom.

A.

$2.116 \text{ Å}$

B.

$1.058 \text{ Å}$

C.

$3.325 \text{ Å}$

D.

$6.65 \text{ Å}$

Q28 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

In third orbit of hydrogen atom wavelength of revolving electron is $\lambda$. Calculate the circumference of third Bohr orbit.

A.

$\lambda$

B.

$3\lambda$

C.

$2\lambda$

D.

$4\lambda$

Q29 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

De-Broglie wavelength of an electron, accelerated by potential $V$ is $\lambda$. What will be de-Broglie wavelength of the electron which is accelerated by $4V$ potential?

A.

$2\lambda$

B.

$4\lambda$

C.

$\frac{\lambda}{2}$

D.

$\frac{\lambda}{4}$

Q30 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

Find the ratio of de Broglie wavelength of molecules of hydrogen and helium which are at temperatures $27^\circ C$ and $127^\circ C$ respectively.

A.

$\sqrt{8}:\sqrt{3}$

B.

$8:3$

C.

$\sqrt{3}:\sqrt{8}$

D.

$3:8$

Correct Answer: A

Explanation:

$\lambda = \frac{h}{\sqrt{3mkT}}$
$\frac{\lambda_{H_2}}{\lambda_{He}} = \sqrt{\frac{m_{He}T_{He}}{m_{H_2}T_{H_2}}}$
$\frac{\lambda_{H_2}}{\lambda_{He}} = \sqrt{\frac{4 \times 400}{2 \times 300}}$
$\frac{\lambda_{H_2}}{\lambda_{He}} = \sqrt{\frac{1600}{600}}$
$\frac{\lambda_{H_2}}{\lambda_{He}} = \sqrt{\frac{8}{3}}$
$\lambda_{H_2}:\lambda_{He} = \sqrt{8}:\sqrt{3}$

Q31 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

A particle of mass $M$ at rest decays into two particles of masses $m_1$ and $m_2$ having non zero velocities. Find out the ratio of the de-Broglie wavelengths of the two particles.

A.

$m_1:m_2$

B.

$1:1$

C.

$m_2:m_1$

D.

$\sqrt{m_1}:\sqrt{m_2}$

Q32 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

Find out velocity of an electron so that its momentum is equal to that of photon with a wavelength of $\lambda = 5200 \text{ Å}$.

A.

$700 \text{ m/s}$

B.

$1400 \text{ m/s}$

C.

$2800 \text{ m/s}$

D.

$1.4 \times 10^6 \text{ m/s}$

Q33 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

Find out voltage applied to an electron microscope to produce electron of wavelength $0.6 \text{ Å}$.

A.

$150 \text{ volt}$

B.

$250 \text{ volt}$

C.

$300 \text{ volt}$

D.

$416.6 \text{ volt}$

Q34 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

What is the effective mass of a photon having wavelength $\lambda$?

A.

$\frac{h}{c\lambda}$

B.

$\frac{hc}{\lambda}$

C.

$\frac{h\lambda}{c}$

D.

$\frac{c\lambda}{h}$

Q35 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

An electron is accelerated by a potential difference of $50$ V. Find the de-Broglie wavelength associated with it.

A.

$0.86$ Å

B.

$2.43$ Å

C.

$1.73$ Å

D.

$3.46$ Å

Q36 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

Find the ratio of de-Broglie wavelength of molecules of hydrogen and helium which are at temperatures $27^\circ C$ and $127^\circ C$ respectively.

A.

$\sqrt{\frac{3}{8}}$

B.

$\sqrt{\frac{8}{3}}$

C.

$\frac{8}{3}$

D.

$\frac{3}{8}$

Q37 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

The de Broglie wavelength $\lambda$ for an electron of energy $150 \text{ eV}$ is

A.

$10^{-8} \text{ m}$

B.

$10^{-10} \text{ m}$

C.

$10^{-12} \text{ m}$

D.

$10^{-14} \text{ m}$

Q38 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

The de Broglie wavelength of particles of mass $m$ with average momentum $p$ at a temperature $T$ in three dimensions is given by

A.

$\lambda = \frac{h}{\sqrt{2 m k_B T}}$

B.

$\lambda = \frac{h}{\sqrt{3 m k_B T}}$

C.

$\lambda = \frac{h}{\sqrt{2 k_B T}}$

D.

$\lambda = \frac{h}{\sqrt{3 m}}$

Q39 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

An electron is moving in Bohr's fourth orbit. Its de Broglie wavelength is $\lambda$. What is the circumference of the 4th orbit?

A.

$2 / \lambda$

B.

$2 \lambda$

C.

$4 \lambda$

D.

$-4 / \lambda$

Q40 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

The velocities of two particles A & B are $0.05 \text{ m/s}$ & $0.02 \text{ m/s}$ respectively. The mass of B is five times of mass of A. The ratio of their de-Broglie wavelength is

A.

$2 : 1$

B.

$1 : 4$

C.

$1 : 1$

D.

$4 : 1$

Q41 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

de-Broglie wavelength of oxygen molecules corresponding to rms velocity

A.

$\frac{h}{\sqrt{m k_B T}}$

B.

$\frac{h}{\sqrt{2 m k_B T}}$

C.

$\frac{h}{\sqrt{3 m k_B T}}$

D.

$\frac{h}{\sqrt{k_B T}}$

Q42 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

The de Broglie wavelength of a proton of energy $E_p$ is twice the de Broglie wavelength of an alpha particle of energy $E_\alpha$. The ratio of $\frac{E_p}{E_\alpha}$ is

A.

$16$

B.

$4$

C.

$1$

D.

$1/4$

Correct Answer: C

Explanation:

$\lambda \propto \frac{1}{\sqrt{m E}}$
$\implies \frac{\lambda_p}{\lambda_\alpha} = \sqrt{\frac{m_\alpha E_\alpha}{m_p E_p}}$
$\implies 4 = \frac{m_\alpha E_\alpha}{m_p E_p}$
$\implies \frac{E_p}{E_\alpha} = 1$

Q43 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

A dust particle of mass $10^{-8} \text{ kg}$ is at room temperature ($300 \text{ K}$). Its de Broglie wavelength is nearest to

A.

$10^{-19} \text{ m}$

B.

$10^{-15} \text{ m}$

C.

$10^{-6} \text{ m}$

D.

$10^{-9} \text{ m}$

Correct Answer: A

Explanation:

$\lambda = \frac{h}{\sqrt{3 m k_B T}}$

Q44 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

The wavelength of a particle of a particle with energy E is proportional to

A.

$1/E$

B.

$1/E^{1/2}$

C.

$E^{1/2}$

D.

$E^2$

Q45 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

The de-Broglie wavelength of an electron with a kinetic energy of $120 \text{ eV}$ is nearly

A.

$1000 \text{ pm}$

B.

$100 \text{ pm}$

C.

$10 \text{ pm}$

D.

$1 \text{ pm}$

Correct Answer: B

Explanation:

$\lambda_{e^-} = \sqrt{\frac{150}{V}} \text{ \AA} = \sqrt{\frac{150}{120}} \text{ \AA}$
$\lambda_{e^-} \approx 1.12 \text{ \AA} = 1.12 \times 10^{-10} \text{ m} = 112 \text{ pm} \approx 100 \text{ pm}$

Q46 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

A particle of mass $M$ at rest decays into two particles of masses $m_1$ and $m_2$ having nonzero velocities. The ratio of de-Broglie wavelengths ($\lambda_1 / \lambda_2$) of particles is

A.

$m_1 / m_2$

B.

$\sqrt{m_2 / m_1}$

C.

$1$

D.

$\sqrt{m_1 / m_2}$

Q47 DPT Dual Nature of Matter MCQ

iCON Education HYD, 79930 92826, 73309 72826 14 Sep 2026

Concept:

The de Broglie wavelength $\lambda$ for an electron of energy 150 eV is

A.

$10^{-8}\text{ m}$

B.

$10^{-10}\text{ m}$

C.

$10^{-12}\text{ m}$

D.

$10^{-14}\text{ m}$

Q48 DPT Bohr's Model MCQ

iCON Education HYD, 79930 92826, 73309 72826 18 Sep 2026

Concept:

The ratio of areas within the electron orbits for the first excited state to the ground state for hydrogen atom is

A.

16: 1

B.

18: 1

C.

4: 1

D.

2: 1

Q49 DPT Bohr's Model MCQ

iCON Education HYD, 79930 92826, 73309 72826 18 Sep 2026

Concept:

The innermost orbit of the hydrogen atom has a diameter 1.06 Å. The diameter of tenth orbit is

A.

5.3 Å

B.

10.6 Å

C.

53 Å

D.

106 Å

Q50 DPT Bohr's Model MCQ

iCON Education HYD, 79930 92826, 73309 72826 18 Sep 2026

Concept:

Energy of the electron in nth orbit of hydrogen atom is given by $E_n = \frac{-13.6}{n^2}$ eV. The amount of energy needed to transfer electron from first orbit to third orbit is

A.

13.6 eV

B.

3.4 eV

C.

12.09 eV

D.

1.51 eV

Physics-II Chapters

Modern Physics

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