Stopping Potential Revisited

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.

Threshold frequency for a metal is ${10}^{15}Hz$. Light of $\lambda =4000\stackrel{\circ }{A}$ falls on its surface. Which of the following statements is correct

1. No photoelectric emission takes place

2. Photo-electrons come out with zero speed

3. Photo-electrons come out with ${10}^3$ m/sec speed
   

4. Photo-electrons come out with ${10}^5$ m/sec speed

Q.

The retarding potential for having zero photo-electron current

1. Is proportional to the wavelength of incident light

2. Increases uniformly with the increase in the wavelength of incident light

3. Is proportional to the frequency of incident light

4. Increases uniformly with the increase in the frequency of incident light wave

Q. The wavelength of a red light is 700 nm. The energy contained in each photon of light is.

1. 4.77 eV
2. 3.77 eV
3. 2.77 eV
4. 1.77 eV

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.

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 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.

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. 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 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.

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.

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.

Light of frequency v is incident on a substance of threshold frequency $v_0(v_0<v)$. The energy of the emitted photo-electron will be

1. $h(v-v_0)$

2. $\frac{h}{v}$

3. $he(v-v_0)$

4. $\frac{h}{v_0}$

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. The relative luminosity of wavelength 600 nm is 0.6. Find the radiant flux of 600 nm needed to produce the same brightness sensation as produced by 120 W of radiant flux at 555 nm.

Q.

Light of frequency v is incident on a substance of threshold frequency $v_0(v_0<v)$. The energy of the emitted photo-electron will be

1. $h(v-v_0)$

2. $\frac{h}{v}$

3. $he(v-v_0)$

4. $\frac{h}{v_0}$

Q.

Light of wavelength $1824\stackrel{\circ }{A}$, incident on the surface of a metal, produces photo-electrons with maximum energy 5.3 eV. When light of wavelength $1216\stackrel{\circ }{A}$ is used, the maximum energy of photoelectrons is 8.7 eV. The work function of the metal surface is

1. 3.5 eV

2. 13.6 eV

3. 6.8 eV

4. 1.5 eV

Q.

Sodium and copper have work functions 2.3eV and 4.5eVrespectively. Then the ratio of their threshold wavelengths is nearest to

1. 1 : 2

2. 4 : 1

3. 2 : 1

4. 1 : 4

Q.

A monochromatic source of light operating at 200 W emits $4\times {10}^{20}$ photons per second. The wavelength of this light will be __ nm.

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.

Light of wavelength $\lambda$ strikes a photo-sensitive surface and electrons are ejected with kinetic energy E. If the kinetic energy is to be increased to 2E, the wavelength must be changed to ${\lambda }^{\prime }$ where

1. ${\lambda }^{\prime }=\frac{\lambda }{2}$

2. ${\lambda }^{\prime }=2\lambda$

3. $\frac{\lambda }{2}<{\lambda }^{\prime }<\lambda$

4. ${\lambda }^{\prime }>\lambda$

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. 2.66 eV

4. 1.07 eV