After traveling through a vacuum a photon of light entering into some transparent denser medium. Thus the energy of light______________?
Correct answer: C. Remains same
- A. Increases because wavelength decreases
- B. Decreases because speed decreases
- C. Remains same
- D. Increases then decrease
Explanation
At a boundary, the photon frequency and hence its energy E = hf remain unchanged, although its speed and wavelength decrease in the denser medium. Thus the reduced speed does not mean reduced photon energy. Students may choose b by assuming energy depends directly on speed rather than on frequency.
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About Photons and the Particle Model of Light
The particle model treats light as photons with energy E equals hf and momentum related to wavelength. Questions involve the photoelectric effect, work function, threshold frequency, stopping potential and photon energy, while distinguishing particle behaviour from the wave description of interference and diffraction.
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