Revision/ Ch 9/ Q8

Revision/ Ch 9/ Q8

  12:18 AM    Rohit

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Q1
A sodium surface is illuminated with light of wavelength 0.300 mm. The work function for sodium is 2.46eV. Calculate
(a)   the energy of each photon in electron volts,
(b)  the maximum kinetic energy of the ejected photoelectrons, and
(c)  the cut off wavelength for sodium.

[4.14 eV, 1.68 eV, 505 nm]

Q2

When monochromatic light of an unknown wavelength falls on a sample of silver, a minimum potential of 2.50 V is required to stop all of the ejected photoelectrons. Determine the

(a)   maximum kinetic energy and
(b)  maximum speed of the ejected photoelectrons.
(c)  Determine the wavelength in nm of the incident light. (The work function for silver is 4.73 
        eV.)

[2.50 eV, 9.37 ´ 10⁵ m/ s, 172 nm]

Q3

When light of wavelength 3.50 ´ 10² nm falls on a potassium surface, electrons having a maximum kinetic energy of 1.31 eV. Find

(a)   the work function of potassium,

(b)  the cutoff wavelength, and

(c)  the frequency corresponding to the cutoff wavelength.

[2.24 eV, 555 nm, 5.41 ´ 10¹⁴ Hz]

Q4

The work function for platinum is 6.35 eV.

(a)   Convert the value of the work function from electron volts to joules.

(b)  Find the cut off frequency for platinum.

(c)  What maximum wavelength of light incident on platinum releases photoelectrons from the 
       platinum’s surface?
(d) If light of energy 8.50 eV is incident on zinc, what is the maximum kinetic energy of the 
       ejected photoelectrons? Give the answer in electron volts.
(e) For photons of energy 8.50 eV, what stopping potential would be required to arrest the 
       current of photoelectrons?

[1.02 ´ 10^-18 J, 1.53 ´ 10¹⁵ Hz, 196 nm, 2.15 eV, 2.15 V]