A researcher studies a pair of closely spaced spectral lines produced by a distant star
PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
A researcher studies a pair of closely spaced spectral lines produced by a distant star. The star emits photons of wavelengths λ1=620nm and λ2=590nm, both measured in vacuum.
(a) Derive a symbolic expression for the difference in energy ΔE between a photon of wavelength λ1 and a photon of wavelength λ2. Your final expression should contain only λ1, λ2, and fundamental constants.
(b) Evaluate ΔE numerically in electron-volts for the given wavelengths. Show your calculations clearly.
(c) The average thermal energy of particles at room temperature is approximately 0.025 eV. Compare your value of ΔE with this thermal energy and discuss whether thermal processes on Earth could readily shift a photon from one of these wavelengths to the other.