Question

60.
h
A plane mirror is placed horizontally on
level ground at a distance of 60m from the
foot of a tower, the light ray from the top of
the tower falling just inside at the edge of
the mirror suffers a deviation of 90°. The
height of tower is
60m
A) 30m B) 60m C) 90m D) 120m
In the above problem, if the eye is 10m above the mirror, then how far is it from the tower?
A) 20m
B)10m
C) 70m
D) none
​

Answer 1

Answer:

The angle subtended at the eye by the top of the tower with respect to the ground os 45 degrees. This happens when the height of the tower is equal to tis distance from the eye. The eye is assumed to be very near to the mirror. (Refer below figure).

Angle subtended by AB = 90 degrees/2 = 45 degrees.

Therefore, tanθ=60h.Thatis,tan45=60h.So,h=60m.

Hence, the height of the tower is 60 m