Question

The following question contains two statements labelled ‘A’ and ‘R’. Examine the each statement carefully and decide, if the assertion ‘A’ and reason ‘R’ are individually correct. If so, decide, whether the reason R is the correct explanation of A. Select your answer, using the options given below.

A : In a periscope two plane mirrors face each other, such that they make an angle of 45°with the periscope tube.

R : The rays of light bend through 90° on striking the plane mirrors.

• A. Both ‘A’ and ‘R’ are correct and ‘R’ is the correct explanation of ‘A’
• B. Both ‘A’ and ‘R’ are correct and ‘R’ is the not correct explanation of ‘A’
• C. ‘A’ is correct, but ‘R’ is incorrect.
• D. 'A’ is incorrect, but ‘R’ is correct.

Answer 1

The correct option is C

‘A’ is correct, but ‘R’ is incorrect.

Explanation for assertion:

1. In a reflecting periscope, two plane mirrors are placed at the bends of the periscope tube at an angle of 45° facing each other.
2. Therefore, the incident light rays strike the mirrors at an angle of 45°.
3. So the light rays after striking these mirrors reflect through an angle of 45° following the law of reflection (angle of incidence = angle of reflection).
4. Thus, the given assertion is correct but the reason is incorrect.

Explanation for reason:

1. The rays of light do not bend through 90° on striking the plane mirrors.
2. The rays bend at an angle of 45° on striking the plane mirrors.

Hence, the correct option is C (‘A’ is correct, but ‘R’ is incorrect.)