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When a surface is irradiated with light ...

When a surface is irradiated with light of wavelength `4950 Å`, a photocurrent appears which vanishes if a retarding potential greater than 0.6 volt is applied across the phototube. When a second source of light is used, it is found that the critical potential is changed to 1.1 volt. The wavelength of the second source is

A

`6150Å`

B

`5150Å`

C

`4150Å`

D

`4500Å`

Text Solution

Verified by Experts

The correct Answer is:
C
`K_2 = 1.1 eV`
`E_2 = W + K_2 = 3.0 eV`
`:. lambda_2 =(12375)/(3.0) = 4125 Å`
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