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NEET2002Chemistrys Block ElementsActual

Assertion : Potassium and caesium are used in photoelectric cells. Reason : Potassium and caesium emit electrons on exposure to light.

Options

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

Correct answer

A. If both the assertion and reason are true and reason is a correct explanation of the assertion.

Step-by-step solution

The valence shell electron in the alkali metals is so loosely held that even the low energy photons (light) can eject this electron from the metal surface. This phenomenon is called as photoelectric effect. K and Cs are used in photoelectric cells which are sensitive to blue light.

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