Question

a ray of light is reflected from a plane mirror so that the angle between the incident and the reflected rays is 60°. If the mirror is rotated to increase the angle of incidence by 3°, what will be the new angle between the incident and reflected rays?

Answer 1

the angle between incident and reflected will be 63degree

Answer 2

The angle between incident ray and normal = the angle between normal and reflected ray !

let angle between incident ray and normal be I,
and angle between normal ray and reflected ray be R,
=> I = R

Now according to data angle between incident ray and normal ray is given as 60°,

We can write angle between incident ray and normal ray as I + R

Now I + R = 60°

But we know that I = R

Now 2I = 60°

I = R = 30°

now when the angle of incidence is increased by 3°,

The new angle of incidence = 30° + 3° = 33°,

The new angle of reflection will also be 33°,

So now the new angle between angle of reflected ray and incident ray is 33°+33°

= 66°,

So the answer is 66° !!