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## Homework Statement

Find the retarding potential required to stop electron of de-broglie wavelength 0.5 nm

## Homework Equations

1)de-broglie wavelenght=h/momentum

2)eV=KE of electron

3)KE=p^2/2m

## The Attempt at a Solution

Using the above three relations is giving me an incorrect answer for V, However in the hint it is mentioned that eV=hc/lambda.

I have four problems- 1)Why are the above relations giving an incorrect answer?

2) hf is the energy of a photon, can we use the same expression for an electron?

3)if yes, How did we obtain this expression?

4)the photon is massless, so is its de-broglie wavelength infinite?

I'd be grateful for your help

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