Problem 3
Monochromatic light in vacuum has frequency f and wavelength λ. A light photon is described using Planck’s constant h and the speed of light c=3.00×10⁸ m/s; ignore interactions with matter. (a) Relate f and λ through wave propagation. (b) Derive one photon’s energy E_γ in terms of f and then λ. (c) Find momentum magnitude p_γ and check dimensions of E_γ and p_γ. Use SI units throughout and treat components as ideal exactly as specified. State sign conventions when writing equations and retain units in final results.
problems.proof.stepOf
problems.proof.analysis
The next part uses the preceding result as input rather than treating parts independently. This keeps conventions and physical state consistent throughout.
problems.proof.pitfall. Pitfall: do not change sign conventions between equations; a negative sign may encode direction rather than an invalid result.