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Yellow light of 557 nm wavelength is inc...

Yellow light of 557 nm wavelength is incident on a cesium surface. It is found that no photo electrons flow in the circuit when the cathode-anode voltage drops below 0.25V. Then the threshold wavelength for photo electric effect from cesium is

A

577 nm

B

653 nm

C

734 nm

D

191 nm

Text Solution

Verified by Experts

The correct Answer is:
B
`(hc)/(lambda) =phi+ev_(s) , phi=2.23 =1.98 eV rArr lambda_(th)=(hc)/(phi)=627 nm`
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