A metallic surface has a threshold frequency of

PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation

Problem

A metallic surface has a threshold frequency of 5.0×1014 Hz5.0\times10^{14}\,\text{Hz}. Five monochromatic radiations of frequencies ν1=6.0×1014 Hz\nu_1=6.0\times10^{14}\,\text{Hz}, ν2=7.5×1014 Hz\nu_2=7.5\times10^{14}\,\text{Hz}, ν3=5.5×1014 Hz\nu_3=5.5\times10^{14}\,\text{Hz}, ν4=4.0×1014 Hz\nu_4=4.0\times10^{14}\,\text{Hz} and ν5=9.0×1014 Hz\nu_5=9.0\times10^{14}\,\text{Hz} are made to fall on this surface one after the other, each with the same intensity. (i) For each of the five radiations, state whether photo–electrons will be emitted from the surface. (ii) Considering only those radiations that do cause emission, arrange them in descending order of the maximum kinetic energy imparted to the emitted electrons. (iii) Give a brief justification for the order obtained in part (ii) without performing any numerical calculation.

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