Question

0ptions are:
a) 45degree
b) 25drgree
c) 75degree
d) all of these​

Answer 1

QUESTION:

Two plane mirrors are arranged at right angles to each other. A ray of light is incident on a horizontal mirror at an angle theta. For what value of theta does the ray emerges parallel to the incoming ray after the reflection from the vertical mirror?

ANSWER:

45°

GIVEN:

Two lines are parallel.

$\theta = \alpha$

TO FIND:

$\theta = ???$

EXPLANATION:

$2 \theta + 2\alpha = 180\:degree\\This\:is \:because\: 2\theta\: and\: 2\alpha \:make \:90\:degree\:with \\ the\:surface\:of\:glass. \\ \theta + \alpha = 90\:degree \\ Substitute\:\alpha = \theta\\ \theta + \theta = 90\:degree\\ 2\theta = 90\:degree \\ \theta = \alpha = 45\:degree$

Conclusion:

$When\:\theta =45\:degree\:the\:angle\:of\:emergence(\alpha)\\will\:also\:be\:equal\:to\:45\:degree.$

NOTE : DIAGRAM IN ATTACHMENT.