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The work functions for sodium and copper...

The work functions for sodium and copper are `2 eV` and `4 eV` . Which of them is suitable for a photocell with `4000 Å` light ?

A

Copper

B

Sodium

C

Both

D

None of these

Text Solution

Verified by Experts

The correct Answer is:
B
Threshold wavelength for `Na` ,
`lambda_(Na) gt (12375)/(2) = 6187.5 Å`
Also `lambda_( cu) = ( 12375)/( 4) = 3093.75`
Since `lambda_(Na) gt 4000 Å` , So `Na` is suitable.
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