Question

It is necessary to illuminate the bottom of a well by reflected solar beam when the light is incident at an angle of $\alpha$=${40}^0$ to the vertical. At what angle $\beta$ to the horizontal should a plane mirror be placed?

• A. ${70}^0$
• B. ${20}^0$
• C. ${50}^0$
• D. ${40}^0$

Answer 1

The correct option is A ${70}^0$

From the figure, it is clear that

$i+r=i+i=140$

or

$i={70}^0$

Thus, plane mirror makes an angle of ${20}^0$ with vertical and ${70}^0$ with horizontal.