Question 9

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 |

Answer

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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