A non relativistic free electron has kinetic energy "K" If its wavelength doubles, its kinetic energy is:
Correct answer: D. K/4
- A. 4K
- B. K/2
- C. 2K
- D. K/4
Explanation
For a free electron, its wavelength increases when its momentum and kinetic energy drop. Since wavelength is inversely related to the square root of kinetic energy, doubling the wavelength makes the energy fall by a factor of four. So the new kinetic energy becomes K/4.
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Atoms emit or absorb light at specific wavelengths because electrons occupy quantized energy levels and change levels by absorbing or releasing photons. The topic covers emission and absorption spectra, spectral series, hydrogen’s line spectrum, energy-level transitions, and the relation between wavelength, frequency and photon energy.
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