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Wave Optics — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsWave Optics1 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 from 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 film which appears bright in reflected system will appear dark in the transmitted light and vice-versa.
Reason (R): The conditions for film to appear bright or dark in reflected light are just reverse to those in the transmitted light.
✓

Answer

  1. Both A and R are true and R is the correct explanation of A.
Explanation:

For reflected system of the film, the maxima or constructive interference is $2\mu\text{t}\cos\text{r}=$ while the maxima for transmitted system of film is given by equation

$2\mu\text{t}\cos\text{r}=\text{n}\lambda$

where t is thickness of the film and r is angle of refraction.

From these two equations we can see that condition for maxima in reflected system and transmitted system are just opposite.

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