MUNISH KAKAR's INSTITUTE OF CHEMISTRY
PHOTOELECTRIC EFFECT WS # 3
Q1.
What happens to kinetic energy of photoelectron when
(a) frequency of radiation is increased
(a) Kinetic energy increases
(b) Wavelength of radiation is increased.
(b) Kinetic energy decreases. If energy is decreased
further photoelectric effect may not be observed
Q2.
Is it possible to change Ionization energy of metal by changing energy of radiation ? No
Q3.
Which in between frequency or intensity can help to increase photoelectric current ?
Intensity, as it helps to generate more number of electrons
Q4.
Among the following given metals, how many metals will be able to show photoelectric
effect when exposed to radiation having wavelength 400 nm ; Erad. = 3.1 eV
A (  = 2.27 eV ) , B (  = 3.5 eV ) , C (  = 3.94 eV ) , D (  = 0.46 eV ) ¸ E (  = 2.13 eV )
F (  = 4.15 eV ) , G (  = 3.03 eV ) , H (  = 4.67 eV )
Q5.
What happens to kinetic energy of photoelectron when ;
(a) Frequency of radiation is doubled
(b) Wavelength of radiation is made one-third ?
(a) Kinetic energy becomes more than double
(b) Kinetic energy becomes more than triple
Q6.
Under which among the following condition (s), photoelectric effect will be observed ?
(a) Frequency of radiation larger than threshold frequency
(b) Wavelength of radiation longer than threshold wavelength
(c) both and b
Q7.
(d) both a and b are incorrect
15
1
Certain metal is exposed to radiation having frequency 3  10 sec , if works function of
such metal is one-third of energy of radiation, calculate ;
(a) Threshold frequency of metal ( 1  1015 )
Q8.
5
(b) Velocity of photoelectron ( appr. 16 10 )
The work function of a metal is 4.0 eV. The longest wavelength of light that can cause
photoelectron emission from the metal is approximately:
(a) 540 nm
Q9.
(b) 400 nm
(c) 300 nm
(d) 220 nm
The work function of a photoelectric material is 3.3 eV, its threshold frequency will be ;
(a) 8 × 1014 Hz
(b) 5 × 1033 Hz
(c) 8 × 1010 Hz
(d) 4 × 1011 Hz
Q10. When light of frequency 3.2 × 1016Hz is used to irradiate a metal surface, the maximum
kinetic energy of the emitted photoelectron is
3
of the energy of the irradiating photon.
4
What is the threshold frequency of the metal ?
(a) 2.4 × 1025 Hz
(b) 2.4 × 1016 Hz
(c) 1.6 × 1015 Hz
(d) 8 × 1015 Hz
Q11. A near UV photon of 300 nm is absorbed by a gas and then re-emitted as two photons.
One photon is red with wavelength 760 nm. Hence wavelength of the second photon is:
(a) 460 nm
(b) 1060 nm
(c) 496 nm
(d) 300 nm
SCO # 203 , SECOND FLOOR , SECTOR - 14 , PKL. 4634812 (O) , 9888019721 , 9988819721
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MUNISH KAKAR's INSTITUTE OF CHEMISTRY
Q12. The work function of a metal is 4.0 eV. The longest wavelength of light that can cause
photoelectron emission from this metal is approximately
(a) 540 nm
(b) 400 nm
(c) 310 nm
(d) 220 nm
Q13. An electron in H-atom in its ground state absorbs 1.50 times as much as energy as the
minimum required for its escape (13.6 eV) from the atom. Thus KE of emitted electron is:
(a) 13.6 eV
(b) 20.4 eV
(c) 34.0 eV
(d) 6.8 eV
Q14. Of the following, radiation with maximum wavelength is:
(a) UV
(b) Radio wave
(c) X-ray
(d) IR
o
Q15. Photoelectric work function of a metal is 1 eV. If a light of wavelength 3000 A falls on the
metal, the velocity of the photoelectron ejected will be
(a) 10 ms-1
(b) 103 ms-1
(c) 104 ms-1
(d) 106 ms-1
Q16. Calculate the energy in kilocalorie per mol of the photons of an electromagnetic radiation
of wavelength 7600 Å.
Ans : 37.58 kcal/mole
Q17. Calculate the kinetic energy of an electron produced in Cs, when it is exposed to radiation
having wavelength 400 nm. Given that the threshold wavelength of Cs is 660 nm.
(1.22eV or 1.95 × 10-19 J )
Q18. When light with a wavelength of 400 nm falls on the surface of sodium, electrons with a
kinetic energy 1.05 x 105 J mol-1 are emitted.
(a) What is the minimum energy needed to remove an electron from sodium ?
(b) What is the maximum  of light that will cause a photoelectron to be emitted ?
19
J
Ans (a) 3.27  10
7
(b) 6.08  10 m
Q19. When light frequency  is shown on metal surface with threshold frequency  o , photo
electrons are emitted with maximum kinetic energy 1.3  1018 J . If  : o  3:1 , calculate
the threshold frequency  o
( 9.81 1014 Hz )
Q20. When a certain metal was irradiated with light of frequency 3.2 x 10 16 Hz, the
photoelectrons emitted had twice the kinetic energy as did photoelectrons emitted when
the same metal was irradiated with light of frequency 2.0 x 1016 Hz. Calculate v0
Ans : 8  1015 Hz
Q21. Yellow light emitted from a sodium lamp has a wavelength () of 580 nm. Calculate the
frequency and wave number of this light.
5.17 x 1014 s1 ; 1.72 x 106 m1
Q22. Calculate (i) wave number (ii) frequency of yellow radiation having  5800 Ǻ.
Ans. (i) 1.724 x 106 m1 (ii) 5.172 x 1014 s1
SCO # 203 , SECOND FLOOR , SECTOR - 14 , PKL. 4634812 (O) , 9888019721 , 9988819721
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MUNISH KAKAR's INSTITUTE OF CHEMISTRY
Q23. A photon of wavelength 4000 Å strikes a metal surface, the work function of the metal
being 2.13 eV. Calculate (i) the energy of the photon in eV, (ii) the kinetic energy of the
emitted photoelectron, and (iii) the velocity of the photoelectron.
Ans : (i) 3.1 eV
(ii) 0.97 eV
(iii) 5.8  105 m / s
Q24. For silver metal, the threshold frequency v0 is 1.13 x 1017 Hz. What is the maximum
kinetic energy of photoelectrons produced by ultraviolet light of wavelength 15.0 Ǻ ?
Ans.=5.652 x 1017 J
SCO # 203 , SECOND FLOOR , SECTOR - 14 , PKL. 4634812 (O) , 9888019721 , 9988819721
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