Question

Light of wavelength 235 nm is incident on Magnesium in a photoelectric effect experiment. The work function of Magnesium is 3.68 eV.

(a) What is the maximum kinetic energy of the emitted electrons, in eV?

(b)What is the maximum velocity of the emitted electrons, in m/s?

(c) What is the stopping potential, in Volts, that results in no collected photoelectrons?

(d) Light of wavelength 235 nm is now incident on lead (work function 5.40 eV). What is the maximum kinetic energy of the emitted electrons, in eV

Answer 1

Solution:

From the information given,

Using photoelectric effect,

a)

K.E_max = E -

= 1240/235 - 3.68 ev

= 5.27 - 3.68

= 1.5965

= 1.60 eV

b) K.E_max = 1.60 eV = 2.56*10^-19 j

1/2*9.11*10^-31 v_max² = 2.56*10^-19

v = 7.5*10⁵ m/s

c) K.E_max = qV

V = 1.60eV/e

= 1.60 V

d)Similarly to part a,

K.E_max = E -

Where

E = 1240/235 = 5.28 <[no electron will be emitted]

K.E_max = 0 eV.

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