A researcher investigates three monochromatic light sources, X, Y
PHYSICS · Multi-part · CBSE · Physics · Dual Nature of Radiation and Matter · Dual Nature of Radiation and Matter
Problem
A researcher investigates three monochromatic light sources, X, Y, and Z, that illuminate identical samples of an unknown metal whose work function is not provided. The measured properties of each light source are listed below.
• Source X: wavelength 380 nm; intensity 2 mW cm⁻²
• Source Y: wavelength 520 nm; intensity 2 mW cm⁻²
• Source Z: wavelength 520 nm; intensity 10 mW cm⁻²
Assume 520 nm lies just above the threshold wavelength for the metal.
(a) Rank the three sources according to the maximum kinetic energy of any emitted electrons, from greatest to least. Clearly indicate any ties and briefly justify your ranking.
(b) Rank the three sources according to the photoelectron emission rate (number of electrons emitted per second), from greatest to least. Clearly indicate any ties and briefly justify your ranking.
(c) Describe qualitatively how the stopping potential for source Z would compare with that for source Y, and explain the physical basis for your comparison.
(d) The researcher doubles the frequency of source Y while keeping its intensity the same by inserting a nonlinear optical crystal that performs frequency doubling. Predict qualitatively the changes, if any, in (i) the emission rate and (ii) the maximum kinetic energy of the emitted electrons. Provide reasoning grounded in the photon model.