Three metals P, Q and R have threshold wavelengths

PHYSICS · Multi-part · CBSE · Physics · Dual Nature of Radiation and Matter · Dual Nature of Radiation and Matter

Problem

Three metals P, Q and R have threshold wavelengths λ0 P=600 nm\lambda_{0\,\text{P}} = 600\,\text{nm}, λ0 Q=400 nm\lambda_{0\,\text{Q}} = 400\,\text{nm} and λ0 R=300 nm\lambda_{0\,\text{R}} = 300\,\text{nm}, respectively. Two monochromatic radiations are available: Radiation A: wavelength 500 nm500\,\text{nm} Radiation B: wavelength 350 nm350\,\text{nm} Both radiations are incident normally and separately on identical samples of the three metals with equal intensities. (i) Convert each threshold wavelength to its corresponding threshold frequency for metals P, Q and R. (ii) When Radiation A is used, identify which metals, if any, emit photo-electrons. For each emitting metal, calculate the stopping potential and arrange the metals in ascending order of this potential. (iii) Repeat part (ii) for Radiation B. (iv) Explain, with reference to your numerical results, why the set of emitting metals and the order of stopping potentials change when the incident radiation is switched from A to B.

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