An atom makes a transition from a state of energy E2 to one of lower energy E1. Which of the following gives the wavelength of the radiation emitted, in terms of the Planck's constant h and the speed of light e?
Correct answer: C. hc/E2-E1
- A. E2-E1/hc
- B. hc/E2-he/E1
- C. hc/E2-E1
- D. c/h(E2-E1)
Explanation
By quantum theory of radiation, the energy change E between energy levels is proportional to the frequency of electromagnetic radiation f and is given by the quantion below E =hf =hc/λ where h is the Planck's constant, c is the speed of light and λ is the wavelength of the radiation. Now, energy change by transition from E2 to E1 is given by E = E2 - E1 E2 - E1 = hc/λ λ = hc/ E2 - E1 Hence, option c is correct.
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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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