The electrons are emitted in the photoelectric effect from a metal surface
(1) Only if the frequency of the incident radiation is above a certain threshold value
(2) Only if the temperature of the surface is high
(3) At a rate that is independent of the nature of the metal
(4) With a maximum velocity proportional to the frequency of the incident radiation
The work function of a metal is 4.2 eV, its threshold wavelength will be:
1. 4000 ˚A
2. 3500 ˚A
3. 2955 ˚A
4. 2500 ˚A
The number of photo-electrons emitted per second from a metal surface increases when:
1. | The energy of incident photons increases. | 2. | The frequency of incident light increases. |
3. | The wavelength of the incident light increases. | 4. | The intensity of the incident light increases. |
The work function of metal is 1 eV. Light of wavelength 3000 Å is incident on this metal surface. The velocity of emitted photo-electrons will be
(a) 10 m/sec (b) 1×103 m/sec
(c) 1×104 m/sec (d) 1×106 m/sec
The work function of a metal is 1.6×10-19 J. When the metal surface is illuminated by the light of wavelength 6400 Å, then the maximum kinetic energy of emitted photo-electrons will be
(Planck's constant = 6.4×10-34 Js)
(a) 14×10-19 J (b) 2.8×10-19 J
(c) 1.4×10-19 J (d) 1.4×10-19 eV
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. 3.2×10-21
2. 3.2×10-19
3. 3.2×10-17
4. 3.2×10-15
The work function for tungsten and sodium are 4.5 eV and 2.3 eV respectively. If the threshold wavelength λ for sodium is 5460 Å, the value of λ for tungsten is
(1) 5893 Å
(2) 10683 Å
(3) 2791 Å
(4) 528 Å
1. | 1.4 eV | 2. | 1.7 eV |
3. | 5.4 eV | 4. | 6.8 eV |
The photoelectric threshold wavelength for a metal surface is 6600 Å. The work function for this is
(1) 1.87 V
(2) 1.87 eV
(3) 18.7 eV
(4) 0.18 eV
Photoelectric effect was successfully explained first by
(1) Planck
(2) Hallwash
(3) Hertz
(4) Einstein