Question

$\huge\frak{\underline{\underline{ \red{Question}}}}$
When a ray of light strikes a plane mirror at an angle of 15° with the mirror, what will be the angle through which the ray gets deviated?​

Answer 1

Answer:

A ray of light that is incident on to the surface of a plane-mirror is reflected with the angle of incidence equal to the angle of reflection. Suppose that the ray had continued, through the mirror, in a straight line it would make an angle θ with the surface of the mirror. The total angle between the straight-line path and the reflected ray is twice the angle of incidence. This is called the deviation of the light and measures the angle at which the light has strayed from its initial straight-line path.

The deviation of a mirror is equal to twice the angle of incidence.

so

Angle of deviation=2°=2×15°=30°

Explanation:

Hope this answer will be helpful..

Answer 2

Before solving the question, let's define some terms.

Angle of Incidence: The angle of incidence refers to the angle formed by the incident ray with the normal at the point of incidence.

Angle of reflection: The angle of reflection refers to the angle formed by the reflected ray with the normal at the point of incidence.

Angle of deviation: Angle of deviation refers to the angle between the extended incident ray and the reflected ray.

These terms are not to be confused with the angle formed by the incident/reflected ray with the surface.

Solution:

Once the ray of light strikes the surface of the mirror making an angle of 15° between the surface and the incident ray, it gets deflected from the mirror by 15° as well.

Let the angle with which the ray strikes the mirror be ACD.

Let the angle with which the ray gets deflected by the mirror be BCE.

In a plane mirror, [Refer to the diagram]

⇒ The angle of deviation of the ray = Angle of deflection + ∠ECF

⇒ The angle of deviation of the ray = 15° + ∠ECF

[∠ECF = ∠ACD = 15° (Vertically opposite angles)]

⇒ The angle of deviation of the ray = 15° + 15°

⇒ The angle of deviation of the ray = 30°

Or, you can directly find the angle by using; Angle of deviation of a ray is equal to twice the angle formed by the ray with the surface of the mirror.

Therefore, Option(b) 30° is the answer.