The Experimental Setup

Q.

What are the five characteristics of light?

Q. Light of wavelength $500nm$ is incident on a metal with a work function of $2.28eV$. The de borglie wavelength of the emitted electron is

1. $\le 2.8\times {10}^{-12}m$
2. $<2.8\times {10}^{-9}m$
3. $<2.8\times {10}^{-10}m$
4. $\ge 2.8\times {10}^{-9}m$

Q. The electric field of a plane electromagnetic wave is given by $\overrightarrow{E}=E_0\hat{i}\cos \left(kz\right)\cos \left(\omega t\right)$
The corresponding magnetic field $\overrightarrow{B}$ is then given by:

1. $\overrightarrow{B}=\frac{E_0}{C}\hat{j}\sin \left(kz\right)\sin \left(\omega t\right)$
2. $\overrightarrow{B}=\frac{E_0}{C}\hat{j}\sin \left(kz\right)\cos \left(\omega t\right)$
3. $\overrightarrow{B}=\frac{E_0}{C}\hat{j}\cos \left(kz\right)\sin \left(\omega t\right)$
4. $\overrightarrow{B}=\frac{E_0}{C}\hat{k}\sin \left(kz\right)\cos \left(\omega t\right)$

Q. Graph between maximum kinetic energy of electron and frequency of incident photon in photoelectric effect is shown. The slope of the curve is

1. Planck’s constant
2. Charge of an electron
3. Work function of metal
4. Ratio of Planck’s constant and charge of electron

Q.

Which of the following phenomena can not be explained by Huygens wave theory?

1. Interference of light

2. Refraction of light

3. Double refraction

4. Reflection of light

Q. The electric field of a plane polarized electromagnetic wave in free space at time $t=0$ is given by an expression $\overrightarrow{E}(x,y)=10\hat{j}\cos \left[\right(6x+8z\left)\right]$. The magnetic field $\overrightarrow{B}(x,z,t)$ is given by

($c$ is the velocity of light)

1. $\frac{1}{c}(6\hat{k}-8\hat{i})\cos \left[\right(6x+8z-10ct\left)\right])$
2. $\frac{1}{c}(4\hat{k}+8\hat{i})\cos \left[\right(2x-8z+20ct\left)\right])$
3. $\frac{1}{c}(5\hat{k}+8\hat{i})\cos \left[\right(6x+8z-80ct\left)\right])$
4. $\frac{1}{c}(4\hat{k}-8\hat{i})\cos \left[\right(6x+8z+70ct\left)\right])$

Q.

The electric field of a plane electromagnetic wave is given by $\overrightarrow{E}=E_{\circ }\left(\hat{x}+\hat{y}\right)\sin (kz-\omega t)$.Its magnetic field will be given by:

1. $\frac{E_{\circ }}{c}\left(\hat{x}+\hat{y}\right)\sin (kz-\omega t)$

2. $\frac{E_{\circ }}{c}\left(\hat{x}-\hat{y}\right)\sin (kz-\omega t)$

3. $\frac{E_{\circ }}{c}\left(\hat{x}-\hat{y}\right)\cos (kz-\omega t)$

4. $\frac{E_{\circ }}{c}\left(-\hat{x}+\hat{y}\right)\sin (kz-\omega t)$

Q.

In a plane electromagnetic wave, the directions of electric field and magnetic field are represented by $\hat{k}$ and $2\hat{i}-2\hat{j}$, respectively. What is the unit vector along the direction of propagation of the wave?

1. $\frac{1}{\sqrt{2}}\left(\hat{i}+\hat{j}\right)$

2. $\frac{1}{\sqrt{5}}\left(2\hat{i}+\hat{j}\right)$

3. $\frac{1}{\sqrt{5}}\left(\hat{i}+2\hat{j}\right)$

4. $\frac{1}{\sqrt{2}}\left(\hat{j}+\hat{k}\right)$

Q. When a certain photosensitive surface is illuminated with monochromatic light of frequency $\nu$, the stopping potential for the photo current is $-V_0/2$. When the surface is illuminated by monochromatic light of frequency $\nu /2$, the stopping potential is $-V_0$. The threshold frequency for photoelectric emission is:

1. $\frac{5\nu }{3}$
2. $2\nu$
3. $\frac{4\nu }{3}$
4. $\frac{3\nu }{2}$

Q. Explain giving reasons for the following :
(a) Photoelectric current in a photocell increases with the increase in the intensity of the incident radiation.
(b) The stopping potential $\left(V_0\right)$ varies linearly with the frequency ($\nu$) of the incident radiation for a given photosensitive surface with the slope remaining the same for different surfaces.
(c) Maximum kinetic energy of the photoelectrons is independent of the intensity of incident radiation.

Q. In an electromagnetic wave the electric field vector and magnetic field vector are given as $\overrightarrow{E}=E_0\hat{i}$ and $\overrightarrow{B}=B_0\hat{k}$ respectively. The direction of propagation of electromagnetic wave is along :

1. $(-\hat{j})$
2. $\left(\hat{k}\right)$
3. $(-\hat{k})$
4. $\hat{j}$

Q.

Why photoelectric effect is not explained in terms of wave theory of light?

Q. The electric and the magnetic field, associated with an electromagnetic wave, propagating along the z-axis, can be represented by

1. $[E=E_0\hat{j},B=B_0\hat{k}]$
2. $[E=E_0\hat{k},B=B_0\hat{i}]$
3. $[E=E_0\hat{j},B=B_0\hat{j}]$
4. $[E=E_0\hat{i},B=B_0\hat{j}]$

Q. 54.The wavelength of K-alpha x rays for lead isotopes pb208, pb206 and pb204 are v1 , v2, and v3 respectiVely then

Q. An electron collides with a fixed hydrogen atom in its ground state. Hydrogen atom is excited and colliding electron loses of its kinetic energy. Consequently, the hydrogen atom may emit a photon corresponding to largest wavelength of the Balmer series. Minimum possible kinetic energy of colliding electron will be

1. 10.2 eV
2. 1.9 eV
3. 12.1 eV
4. 1.3 eV

Q. 1. The energy stored in 4uF capacitor is

Q. An electron beam has an aperture $1m{m}^2$. A total of $6.0\times {10}^{16}$ electrons go through any perpendicular cross-section per second. Find the current density in the beam.

1. $7.6\times {10}^{3}A{m}^{-2}$
2. $9.6\times {10}^{3}A{m}^{-2}$
3. $8.6\times {10}^{3}A{m}^{-2}$
4. $6.6\times {10}^{3}A{m}^{-2}$

Q.

In an experiment on photo electric effect, light of wavelength 400 nm is incident on a cesium plate at the rate of 5.0 W. The potential of the collector plate is made sufficiently positive with respect to the emitter so that the current reaches its saturation value. Assuming that on the average one out of every ${10}^6$ photons is able to eject a photo electron, find the photo current in the circuit.

Q. a capacitor with plate separation d is charged to V volts. the battery is disconnected and a dielectric slab of thickness d/2 and dielectric constant 2 is inserted between the plates. The potential difference across its terminal becomes

Q.

Does electric current (both dc and ac) flow through the surface of a conductor or through the space in the conductor??

Q. The maximum velocity of electrons emitted from a metal surface is $V$. When frequency of light falling on it is $f$. The maximum velocity when frequency becomes $4f$ is

1. $>2V$
2. $<2V$
3. Between $2V$ 𝑎𝑛𝑑 $4V$
4. $2V$

Q. The time taken by a photoelectron to come out after the photon strikes is approximately

1. ${10}^{-4}s$
2. ${10}^{-10}s$
3. ${10}^{-16}$
4. ${10}^{-1}s$

Q. A photon and electron both have same energy $E_0=100eV$, then

1. both have same wavelength
2. photon has longer wavelength
3. electron has longer wavelength
4. electron has lesser momentum

Q. Which of the following statements is(are) correct according to the wave theory of light?

1. A radiation with any frequency will cause photoelectric effect.
2. Maximum kinetic energy of photoelectrons will depend on the intensity of radiation.
3. Wave theory predicts appreciable time lag with less intense radiation.
4. Maximum kinetic energy of photoelectrons will depend on frequency of radiation.

Q.

What is the significance of the Fresnel Kirchhoff diffraction formula?

Q. Energy conversion in a photoelectric cell takes place from

1. Chemical to electrical
2. Magnetic to electrical
3. Optical to electrical
4. Mechanical to electrical

Q. What is a photoelectric effect? Write any three laws of the photoelectric effect. Explain these laws by Einstein's equation of the photoelectric effect.

Q. If the frequency of light in a photoelectric experiment is doubled then maximum kinetic energy of photo electron.

1. be doubled
2. be halved
3. becomes more than double
4. become less than double

Q. The electric field of a radio wave is given by $\overrightarrow{E}=E_0\sin (kz-\omega t)(\hat{i}+\hat{j}).$ Give a unit vector in the direction of the magnetic field at a place and time where $\sin (kz-\omega t)$ is positive.

1. $\frac{(\hat{i}+\hat{k})}{\sqrt{2}}$
2. $\frac{(-\hat{i}-\hat{k})}{\sqrt{2}}$
3. $\frac{-\hat{i}+\hat{j}}{\sqrt{2}}$
4. $\frac{\hat{i}-\hat{k}}{\sqrt{2}}$

Q.

The ratio of energies of two different radiations whose frequencies are $3\mathrm{x}{10}^{14}\mathrm{Hz}$ and $5\mathrm{x}{10}^{14}\mathrm{Hz}$ is ______ .