For photoelectric emission from certain metal the cut-off frequency is v. If radiation of frequency 2v impinges on the metal plate, the maximum possible velocity of the emitted electron will be (m is the electron mass)

Options

(a) √ hv / m
(b) √ 2hv / m
(c) 2 √hv / m
(d) √ hv / (2m)

Correct Answer:

√ 2hv / m

Explanation:

From photo-electric equation,
hv’ = hv + Kₘₐₓ …(i)
h.2v = hv + 1/2 mV²ₘₐₓ [ v’ = 2v ]
hv = 1/2 mV²ₘₐₓ ⇒ Vₘₐₓ = √ 2hv / m