Question

An electron of mass $m$ and magnitude of charge $e$ at rest, gets accelerated by a constant electric field $E$. The rate of change of de-Broglie wavelength of this electron at a time $t$ is (ignore relativistic effects)

JEE Main 2020 (09 Jan Shift 2)

Options

• A: $\frac{d\lambda }{dt}=-\frac{h}{eEt}$
• B: $\frac{d\lambda }{dt}=-\frac{2h}{eEt}$
• C: $\frac{d\lambda }{dt}=-\frac{2h}{eE{t}^2}$
• D: $\frac{d\lambda }{dt}=-\frac{h}{eE{t}^2}$

Question

An electron (mass $\mathrm{m}$ ) with initial velocity $\overrightarrow{v}=v_0\widehat{i}+v_0\widehat{j}$ is in an electric filed $\overrightarrow{E}=-E_0\widehat{k}.$ If ${\lambda }_0$ is initial de-Broglie wavelength of electron, its de-Broglie wave length at time $t$ is given by:

JEE Main 2020 (08 Jan Shift 2)

Options

• A: $\frac{{\lambda }_0\sqrt{2}}{\sqrt{1+\frac{e^2{E}^2{t}^2}{m^2{v}_0^2}}}$
• B: $\frac{{\lambda }_0}{\sqrt{1+\frac{e^2{E}^2{t}^2}{m^2{v}_0^2}}}$
• C: $\frac{{\lambda }_0}{\sqrt{1+\frac{e^2{E}^2{t}^2}{2m^2{v}_0^2}}}$
• D: $\frac{{\lambda }_0}{\sqrt{2+\frac{e^2{E}^2{t}^2}{m^2{v}_0^2}}}$

Question

Two identical photocathodes receive the light of frequencies $f_1$ and $f_{\mathit{2}}$ respectively. If the velocities of the photo-electrons coming out are $v_{\mathit{1}}$ and $v_2$ respectively, then

JEE Main 2021 (17 Mar Shift 2)

Options

• A: $v_{\mathit{1}}^{\mathit{2}}\mathit{-}{v}_{\mathit{2}}^{\mathit{2}}\mathit{=}\frac{\mathit{2}\mathit{ }\mathit{h}}{\mathit{ }\mathit{m}}[f_1-f_2]$
• B: $v_1^2+v_2^2=\frac{2h}{m}\left[f_1+f_2\right]$
• C: $v_1+v_2={\left[\frac{2 h}{ m}\left(f_1+f_2\right)\right]}^{\frac{1}{2}}$
• D: $v_1-v_2={\left[\frac{2 h}{ m}\left(f_1-f_2\right)\right]}^{\frac{1}{2}}$

Question

An electron having de-Broglie wavelength $\lambda$ is incident on a target in a $X$-ray tube. Cut-off wavelength of emitted $X$-ray is:

JEE Main 2021 (20 Jul Shift 2)

Options

• A: $0$
• B: $\frac{2{ m}^2{c}^2{\lambda }^2}{{ h}^2}$
• C: $\frac{2mc{\lambda }^2}{ h}$
• D: $\frac{hc}{mc}$

Question

A certain metallic surface is illuminated by monochromatic radiation of wavelength $\lambda$. The stopping potential for photoelectric current for this radiation is $3{\mathit{ }\mathit{V}}_0.$ If the same surface is illuminated with a radiation of wavelength $2\lambda ,$ the stopping potential is $V_0.$ The threshold wavelength of this surface for photoelectric effect is___________$\lambda .$

JEE Main 2021 (20 Jul Shift 2)

Enter your answer

Question

A metal exposed to light of wavelength $800 \mathrm{nm}$ and emits photoelectrons with a certain kinetic energy. The maximum kinetic energy of photo-electron doubles when light of wavelength $500 \mathrm{nm}$ is used. The work function of the metal is

(Take $hc=1230 \mathrm{eV}-\mathrm{nm}$).

JEE Main 2022 (25 Jul Shift 1)

Options

• A: $1.537\mathrm{eV}$
• B: $2.46\mathrm{eV}$
• C: $0.615\mathrm{eV}$
• D: $1.23\mathrm{eV}$

Question

A parallel beam of light of wavelength $900 \mathrm{nm}$ and intensity $100{\mathrm{Wm}}^{-2}$ is incident on a surface perpendicular to the beam. The number of photons crossing $1{ \mathrm{cm}}^2$ area perpendicular to the beam in one second is

JEE Main 2022 (26 Jul Shift 1)

Options

• A: $3\times {10}^{16}$
• B: $4.5\times {10}^{16}$
• C: $4.5\times {10}^{17}$
• D: $4.5\times {10}^{20}$

Question

An $\alpha$ particle and a proton are accelerated from rest through the same potential difference. The ratio of linear momenta acquired by above two particals will be :

JEE Main 2022 (29 Jul Shift 2)

Options

• A: $\sqrt{2}:1$
• B: $2\sqrt{2}:1$
• C: $4\sqrt{2}:1$
• D: $8:1$

Question

An electron (mass $m$) with an initial velocity $\overrightarrow{v}=v_0\hat{i}\left(v_0>0\right)$ is moving in an electric field $\overrightarrow{E}=-E_0\hat{i}\left(E_0>0\right)$ where $E_0$ is constant. If at $t=0$, de-Broglie wavelength is ${\lambda }_0=\frac{h}{m{v}_0}$, then its de-Broglie wavelength after time $t$ is given by

JEE Main 2022 (27 Jul Shift 1)

Options

• A: ${\lambda }_0$
• B: ${\lambda }_0\left(1+\frac{e{E}_{0}t}{m{v}_0}\right)$
• C: ${\lambda }_{0}t$
• D: $\frac{{\lambda }_0}{\left(1+\frac{e{E}_{0}t}{m{v}_0}\right)}$

Question

The electric field at a point associated with a light wave is given by
$E=200\left[\sin \left(6\times {10}^{15}\right)t+\sin \left(9\times {10}^{15}\right)t\right] {\mathrm{Vm}}^{-1}$

Given: $h=4.14\times {10}^{-15} \mathrm{eVs}$

If this light falls on a metal surface having a work function of $2.50 \mathrm{eV}$, the maximum kinetic energy of the photoelectrons will be

JEE Main 2022 (29 Jun Shift 2)

Options

• A: $1.90 \mathrm{eV}$
• B: $3.27 \mathrm{eV}$
• C: $3.60 \mathrm{eV}$
• D: $3.42 \mathrm{eV}$

Question

In photoelectric effect
A. The photocurrent is proportional to the intensity of the incident radiation.
B. Maximum kinetic energy with which photoelectrons are emitted depends on the intensity of incident light.
C. Max K.E. with which photoelectrons are emitted depends on the frequency of incident light.
D. The emission of photoelectrons require a minimum threshold intensity of incident radiation.
E. Max K.E. of the photoelectrons is independent of the frequency of the incident light.
Choose the correct answer from the options given below:

JEE Main 2023 (08 Apr Shift 2)

Options

• A: $\mathrm{A}$ and $\mathrm{B}$ only
• B: $\mathrm{A}$ and $\mathrm{E}$ only
• C: $\mathrm{A}$ and $\mathrm{C}$ only
• D: $\mathrm{B}$ and $\mathrm{C}$ only

Question

Which figure shows the correct variation of applied potential difference (V) with photoelectric current (I) at two different intensities of light $\left(\mathrm{I}_1 < \mathrm{I}_2\right)$ of same wavelengths :

JEE Main 2024 (04 Apr Shift 1)

Options

• A:
  
• B:
  
• C:
  
• D:
  

Question

Given below are two statements : Statement I : Figure shows the variation of stopping potential with frequency $(v)$ for the two photosensitive materials $\mathrm{M}_1$ and $\mathrm{M}_2$. The slope gives value of $\frac{\mathrm{h}}{\mathrm{e}}$, where $\mathrm{h}$ is Planck's constant, $\mathrm{e}$ is the charge of electron. Statement II : $\mathrm{M}_2$ will emit photoelectrons of greater kinetic energy for the incident radiation having same frequency. In the light of the above statements, choose the most appropriate answer from the options given below.

JEE Main 2024 (05 Apr Shift 1)

Options

• A: Both Statement I and Statement II are correct
• B: Statement I is incorrect but Statement II is correct
• C: Both Statement I and Statement II are incorrect
• D: Statement I is correct and Statement II is incorrect

Question

Which of the following phenomena does not explain by wave nature of light. A. reflection B. diffraction C. photoelectric effect D. interference E. polarization Choose the most appropriate answer from the options given below:

JEE Main 2024 (06 Apr Shift 1)

Options

• A: E only
• B: B, D only
• C: C only
• D: A, C only

Question

Average force exerted on a non-reflecting surface at normal incidence is $2.4 \times 10^{-4} \mathrm{~N}$. If $360 \mathrm{~W} / \mathrm{cm}^2$ is the light energy flux during span of 1 hour 30 minutes, Then the area of the surface is:

JEE Main 2024 (08 Apr Shift 1)

Options

• A: $0.2 \mathrm{~m}^2$
• B: $20 \mathrm{~m}^2$
• C: $0.1 \mathrm{~m}^2$
• D: $0.02 \mathrm{~m}^2$

Question

The de-Broglie wavelength of an electron is the same as that of a photon. If velocity of electron is $25\%$ of the velocity of light, then the ratio of K.E. of electron and K.E. of photon will be:

JEE Main 2024 (29 Jan Shift 1)

Options

• A: $\frac{1}{1}$
• B: $\frac{1}{8}$
• C: $\frac{8}{1}$
• D: $\frac{1}{4}$

Question

When a metal surface is illuminated by light of wavelength $\lambda$, the stopping potential is $8 \mathrm{V}$. When the same surface is illuminated by light of wavelength $3\lambda$, stopping potential is $2 \mathrm{V}$. The threshold wavelength for this surface is :

JEE Main 2024 (31 Jan Shift 1)

Options

• A: $5\lambda$
• B: $3\lambda$
• C: $9\lambda$
• D: $4.5\lambda$

Question

In a photoelectric effect experiment a light of frequency $1.5$ times the threshold frequency is made to fall on the surface of photosensitive material. Now if the frequency is halved and intensity is doubled, the number of photo electrons emitted will be:

JEE Main 2024 (31 Jan Shift 2)

Options

• A: Doubled
• B: Quadrupled
• C: Zero
• D: Halved