Stopping Potential Revisited

Q. Light of wavelength $4000\stackrel{\circ }{A}$ falls on a photosensitive metal and a negative 2V potential stops the emitted electrons. The work function of the material (in eV) is approximately $(h=6.6\times {10}^{-34}Js,e=1.6\times {10}^{-19}C,c=3\times {10}^{8}m{s}^{-1})$

1. 1.1
2. 2
3. 2.2
4. 3.1

Q. The work function of a metallic surface is 5.01 eV. The photo-electrons are emitted when light of wavelength $2000\stackrel{\circ }{A}$ falls on it. The potential difference applied to stop the fastest photo-electrons is
$[h=4.14\times {10}^{-15}eVsec]$

1. 1.2 volts
2. 3.6 volts
3. 2.24 volts
4. 4.8 volts

Q.

The work functions for sodium and copper are 2eV and 4eV. Which of them is suitable for a photocell with $4000\stackrel{\circ }{A}$ light

1. Copper

2. Sodium

3. Both

4. Neither of them

Q.

If work function of metal is 3eVthen threshold wavelength will be

1. $4125\stackrel{\circ }{A}$

2. $4000\stackrel{\circ }{A}$

3. $4500\stackrel{\circ }{A}$

4. $5000\stackrel{\circ }{A}$

Q.

The light rays having photons of energy 1.8 eV are falling on a metal surface having a work function 1.2 eV. What is the stopping potential to be applied to stop the emitting electrons

1. 3 eV

2. 0.6 eV

3. 1.2 eV

4. 1.4 eV

Q.

Light of wavelength $4000\stackrel{\circ }{A}$ is incident on a sodium surface for which the threshold wave length of photo – electrons is $5420\stackrel{\circ }{A}$. The work function of sodium is

1. 4.58 eV

2. 2.29 eV

3. 1.14 eV

4. 0.57 eV

Q.

Photon of 5.5 eV energy fall on the surface of the metal emitting photoelectrons of maximum kinetic energy 4.0 eV. The stopping voltage required for these electrons are

1. 5.5 V

2. 1.5 V

3. 9.5 V

4. 4.0 V

Q.

If the energy of a photon corresponding to a wavelength of $6000\stackrel{\circ }{A}is3.32\times {10}^{-19}J$, the photon energy for a wavelength of $4000\stackrel{\circ }{A}$ will be

1. 1.4 eV

2. 3.1 eV

3. 4.9 eV

4. 1.6 eV

Q.

Which of the following statement is not correct

1. Photographic plates are sensitive to infrared rays

2. Photographic plates are sensitive to ultraviolet rays

3. Infra-red rays are invisible but can cast shadows like visible light

4. Infrared photons have more energy than photons of visible light

Q.

In a photoelectric experiment for $4000\stackrel{\circ }{A}$
incident radiation, the potential difference to stop the ejection is 2 V. If the incident light is changed to $3000\stackrel{\circ }{A}$
, then the potential required to stop the ejection of electrons will be

1. 2 V

2. Less than 2 V

3. Zero

4. Greater than 2 V

Q. The work functions of metals A and B are in the ratio 1 : 2. If light of frequencies f and 2f are incident on the surfaces of A and B respectively, the ratio of the maximum kinetic energies of photoelectrons emitted is (f is greater than threshold frequency of A, 2f is greater than threshold frequency of B)

1. 1 : 1
2. 1 : 2
3. 1 : 3
4. 1 : 4

Q.

Light from a bulb is falling on a wooden table but no photoelectrons are emitted. Why?

Q.

A photocell stops emission if it is maintained at 2V negative potential. The energy of most energetic photoelectron is

1. 2eV

2. 2J

3. 2kJ

4. 2keV

Q. A parallel beam of light of intensity $I$ and cross section area $S$ is incident on a plate at normal incidence. The photoelectric emission efficiency is $100\%$, the frequency of beam is $v$ and the work function of the plate is $\varphi (hv>\varphi )$. Assuming all the electrons are ejected normal to the plane and with same maximum possible speed. The net force exerted on the plate only due to striking of photons and subsequent emission of electron is

1. $\frac{IS}{hv}\left(\frac{2h}{\lambda }\sqrt{hv-\varphi }\right)$
2. $\frac{2IS}{hv}(\frac{h}{\lambda }+\sqrt{2m(hv-\varphi )})$
3. $\frac{IS}{hv}(\frac{h}{\lambda }+\sqrt{2m(hv-\varphi )})$
4. $\frac{2IS}{hv}(\frac{h}{\lambda }+\sqrt{m(hv-\varphi )})$

Q. A point source of light is used in a photoelectric experiment. If the source is moved farther from the emitting metal, the stopping potential .

1. will increase
2. will decrease
3. will remain constant

Q.

The maximum wavelength of radiation that can produce photoelectric effect in a certain metal is 200 nm. The maximum kinetic energy acquired by electron due to radiation of wavelength 100 nm will be

1. 12.4 eV

2. 6.2 eV

3. 100 eV

4. 200 eV

Q.

When light falls on a metal surface, the maximum kinetic energy of the emitted photo-electrons depends upon

1. The time for which light falls on the metal

2. Frequency of the incident light

3. Intensity of the incident light

4. Velocity of the incident light

Q.

A metal surface of work function 1.07 eV is irradiated with light of wavelength 332 nm. The retarding potential required to stop the escape of photo-electrons is

1. 4.81 eV

2. 3.74 eV

3. 1.07 eV

4. 2.66 eV

Q.

Ultraviolet radiations of 6.2 eV falls on an aluminium surface (work function 4.2 eV). The kinetic energy in joules of the fastest electron emitted is approximately

1. $3.2\times {10}^{-21}$

2. $3.2\times {10}^{-19}$

3. $3.2\times {10}^{-15}$

4. $3.2\times {10}^{-17}$

Q.

Light of frequency v is incident on a certain photoelectric substance with threshold frequency $v_0$. The work function for the substance is

1. $hv$

2. $h{v}_0$

3. $h(v-v_0)$

4. $h(v+v_0)$

Q.

Threshold wavelength for photoelectric effect on sodium is 5000 $\stackrel{\circ }{A}$. Its work function is

1. $15J$

2. $4\times {10}^{-81}J$

3. $16\times {10}^{-14}J$

4. $4\times {10}^{-19}J$

Q.

When a metal surface is illuminated by light of wavelengths 400 nm and 250 nm, the maximum velocities of the photoelectrons ejected are vand 2v respectively. The work function of the metal is (h = Planck’s constant, c = velocity of light in air)

1. $2hc\times {10}^{6}J$

2. $1.5hc\times {10}^{6}J$

3. $hc\times {10}^{6}J$

4. $0.5hc\times {10}^{6}J$

Q.

If in a photoelectric experiment, the wavelength of incident radiation is reduced from 6000 $A^{\circ }$ to 4000 $A^{\circ }$ then

1. Stopping potential will decrease

2. Stopping potential will increase

3. Kinetic energy of emitted electrons will decrease

4. The value of work function will decrease

Q.

4 eV is the energy of the incident photon and the work function in 2eV.What is the stopping potential

1. $2V$

2. $4V$

3. $6V$

4. $2\sqrt{2}V$

Q. The minimum wavelength of photon is $5000\stackrel{\circ }{A}$ , its energy will be

1. 2.5 eV
2. 50 V
3. 5.48 eV
4. 7.48 eV

Q.

Kinetic energy with which the electrons are emitted from the metal surface due to photoelectric effect is

1. Independent of the intensity of illumination

2. Independent of the frequency of light

3. Inversely proportional to the intensity of illumination

4. Directly proportional to the intensity of illumination

Q.

Kinetic energy with which the electrons are emitted from the metal surface due to photoelectric effect is

1. Independent of the intensity of illumination

2. Independent of the frequency of light

3. Inversely proportional to the intensity of illumination

4. Directly proportional to the intensity of illumination

Q.

When light falls on a metal surface, the maximum kinetic energy of the emitted photo-electrons depends upon

1. The time for which light falls on the metal

2. Frequency of the incident light

3. Intensity of the incident light

4. Velocity of the incident light

Q.

Light of wavelength 5000 $\stackrel{\circ }{A}$ falls on a sensitive plate with photoelectric work function of 1.9 eV. The kinetic energy of the photoelectron emitted will be

1. 0.58 eV

2. 2.48 eV

3. 1.24 eV

4. 1.16 eV

Q.

Threshold wavelength for photoelectric effect on sodium is 5000 $\stackrel{\circ }{A}$. Its work function is

1. $15J$

2. $16\times {10}^{-14}J$

3. $4\times {10}^{-19}J$

4. $4\times {10}^{-81}J$