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12th Class Physics Ray Optics Question Bank MCQs - Ray Optics and Optical Instruments

  • question_answer
    A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first color to emerge is

    A) blue

    B) green

    C) violet

    D) red

    Correct Answer: D

    Solution :

    Option [d] is correct
    Explanation: As we know that the velocity of wave is: \[v=\operatorname{v}\lambda \]
    When light ray goes from one medium to other medium, the frequency of light remains unchanged.
    So, \[v\propto \lambda \] or greater the wavelength, greater the speed.
    And, the light of red color is of highest wavelength and therefore of highest speed. So, I after travelling through the slab, the red color emerges first.


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