Let an electron beam be accelerated by adjustable potential V. If we decrease potential V, the wavelength of the matter wave associated with the electron will:
Correct answer: A. increase
- A. increase
- B. decrease
- C. remain the same
- D. sometimes increase sometimes decrease
Explanation
Decreasing potential reduces the electron's kinetic energy and momentum.By De Broglie's equation (λ = h/p), lower momentum implies a longer wavelength. Thus, wavelength increases.
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About Dawn of Modern Physics
Classical physics cannot explain blackbody radiation and related observations, leading to Planck’s quantum theory, in which energy is emitted or absorbed in discrete packets. Photons provide the particle model of light, with energy and momentum linked to frequency and wavelength, including the photoelectric effect and its threshold frequency.
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