Question

(D)
19
Two vertical plane mirrors are inclined
at an angle of 60° with each other. A ray
of light travelling horizontally is reflected
first from one mirror and then from the
other. The resultant deviation of the ray
is :​

Answer 1

Answer:

Fromthefigure

a+b=90

0

⇒b=90

0

−a

Now,

b+60+c=180

⇒c=180−60−b

=180−(90−a)

=30+a

Now,

d+c=90

d=90−c

=90−(30+a)

=60−a

Thus,intrianglePQR

∠Q=2a

∠R=2d=2(60−a)=120−2a

so,angle∠QPTis=∠Q+∠R=120

Now,

angleofdeviation=reflex∠QPT

=360−120

=240∘

bye