Question

9.If a beam of light is incident at an angle of 40 degree with the mirror, what will be the angle between the incident and the reflected beam

Answer 1

Angle between incident & reflected rays is 80 degree.

Incident angle = angle of incident ray to the normal.

Reflections angle=Angle of reflected ray to normal.

For any mirror, incident angle= reflections angle.

Angle between incident & reflections rays = incident angle + reflections = 40 + 40 = 80 degree.

Answer 2

Working out:

In the above question, we are given with a ray diagram where we will draw this with all the elements like incident ray, normal and reflected ray.

► Refer to the attachment....

We know that normal is perpendicular to the surface of mirror, So we can say that:

• Angle made by incident ray with normal + Angle made by incident ray with mirror = 90°

GiveN:

• Angle by Incident ray with mirror = 40°

By using the above relation,

⇛ Angle made by incident ray with normal + 40° = 90°

⇛ Angle made by incident ray with mirror = 50°

Now according to laws of reflection:

• Angle of incidence = Angle of reflection

So, Angle between Incident ray and Reflected Ray = 2(Angle of incidence/Angle made by incident ray with normal)

⇛ Angle between Incident ray and Reflected Ray = 2(50°)

⇛ Angle between Incident ray and Reflected Ray = 100°

So the required angle is:

$\huge{ \boxed{ \sf{ \purple{100 \degree}}}}$

And we are done !!

Explore more !!

• Angle made by Incident ray with mirror = Glance Angle of incidence.
• Angle made by Incident ray with normal = Angle of incidence