Question

A certain metal when irradiated to light `(v = 3.2 xx 10^(16) Hz)` emits photoelectrons with twice kinetic energy as did photoelectrons when the same metal is irradiation by light `( v = 2.0 xx 10^(16)Hz)`. The `v_(0)` Threshold frequency ) of the metal is
A. `1.2xx10^(14)`Hz
B. `8xx10^(15)` Hz
C. `1.2xx10^(16)` Hz
D. `4xx10^(12)` Hz

Answer 1

Correct Answer - B
`(K.E)_(1)=hv_(1)-hv_(0)
(K.E)_(2)=hv_(2)-hv_(0)
As" "(K.E)_(1)=2xx(K.E)_(2)
therefore" "(hv_(1)-hv_(0))=2(hv_(2)-hv_(0))
or" "v_(0)=2v_(2)-v_(1)=2xx(2xx10^(16))-(3.2xx10^(16))
=0.8xx10^(16)Hz or 8xx10^(15)Hz`