photoelectric-effect and stopping potential?

Question

1. In a photoelectric-effect experiment, light of wavelength 420 nm is incident on a sample of sodium. The work function of sodium is 3.67 x 10^-19 J.Calculate the stopping potential required to just stop all electrons from reaching the anode.

2. Light of a different wavelength is incident on a sample of calcium (work function 4.65 x 10^-19 J) The same stopping potential as in (1) is required to just stop all electrons from reaching the anode. Is the wavelength in this case bigger or smaller than in (1) Justify your answer.

Answer 1

Vq = (hc / λ) - W
1) 0.67V
2)348nm

the end

Answer 2

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