When a light of a given wavelength falls on a metallic surface the stopping potential for photoelectrons is 3.2 V. If a second light having wavelength twice of first light is used, the stopping potential drops to 0.7 V. The wavelength of first light is 
m. ( 
)
A
B
C
D
Text Solution
Verified by ExpertsThe correct answer is:
A
Using Einstein's photoelectric equation with stopping potentials:
For first light, 
.
For second light with 
(so 
): 
.
From given values: 
gives 
.
Thus 
.
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