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Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsDual Nature of Radiation and Matter1 Mark
Question
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions front the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): The threshold frequency of photoelectric effect supports the particle nature of light.
Reason (R): If frequency of incident light is less than the threshold frequency, electrons are not emitted from metal surface.
✓

Answer

  1. Both A and R are true but R is NOT the correct explanation of A.
Explanation:
There is no emission of photoelectrons till the frequency of incident light is less than a minimum frequency, however intense light it may be.ln photoelectric effect, it is a single particle collision. Intensity is $\text{h}\upsilon\times\text{N},$ where hu is the individual energy of the photon and N is the total number of photon. ln the wave theory, the intensity is proportional, not only to $\upsilon^2$ but also to the square of amplitude. For the same frequency, increase in intensity only increase the number of photons (in the quantum theory of Einstein).

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