Q62 · UPPSC Prelims 2018 · Set B · General Studies

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Which of the following electro magnetic radiations has the maximum energy?

A Visible light
B Infrared rays
C Ultraviolet rays
D X-rays

Correct answer: (d) X-rays

Explanation

  1. A

    Visible light

    Visible light is a narrow mid-band of the electromagnetic spectrum. Its photons carry less energy than ultraviolet or X-ray photons. This option is not the key.

  2. B

    Infrared rays

    Infrared rays have longer wavelength and lower frequency than visible light, so still less energy per photon. This option is therefore wrong.

  3. C

    Ultraviolet rays

    Ultraviolet rays are more energetic than visible light but less energetic than X-rays of typical diagnostic and hard bands. Among the four listed, ultraviolet is not the maximum. This option is not the key.

  4. D

    X-rays

    X-rays have shorter wavelength and higher frequency than ultraviolet, so the highest photon energy in this list. Energy of a photon rises with frequency. This option is the official key.

Summary. Official key is (d) X-rays. Photon energy increases from infrared through visible and ultraviolet to X-rays. Gamma rays would be higher still, but they are not among the options. Visible and infrared are too soft; ultraviolet is intermediate. Only X-rays have the maximum energy here.