12th Physics 2018 Set1 Delhi Board Paper Solution
If light of wavelength 412.5 nm is incident on each of the the metals given below, which ones will show photoelectric emission and why?
| Metal | Work Function |
| Na | 1.92 |
| K | 2.15 |
| Ca | 3.20 |
| Mo | 4.17 |
A metal will show photoelectric emission in below situation:
E ≥ work funciton
Now according to the relation below:
E = h (c/λ)
E = 1240 / λ
λ = 1240 /412.5 nm
λ = 3.006 eV
So here, work function of k and Na are less than incident energy of photon. Hence, only potassium (k) and Sodium (Na) will show photoelectic emission.
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