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NEET2013PhysicsElectromagnetic WavesActual

Assertion : A laser beam of 0.2 ~W power can drill holes through a metal sheet, whereas a 1000 ~W torch-light cannot. Reason : The frequency of laser light is much higher than that of torch light.

Options

  1. AIf both assertion and reason are true and reason is the correct explanation of assertion.
  2. BIf both assertion and reason are true but reason is not the correct explanation of assertion.
  3. CIf assertion is true but reason is false.
  4. DIf both assertion and reason are false.

Correct answer

C. If assertion is true but reason is false.

Step-by-step solution

A laser is a highly monochromatic and nearperfect parallel beam of light, due to which the beam can be focussed by a converging lens to a very small spot. As the intensity of the beam is too high, it can drill holes through a metal sheet even if the power is 0.2 ~W . But even a torch-light of 1000 ~W power cannot drill holes in such a metal sheet, because the light is less intense and the beam is not parallel.

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