Reflection of light class 10

Reflection of light

When a ray or beam of light incident on a polished or smooth interface, it bounces back into the same medium. This phenomenon of light is known as the Reflection of light.

Observe the figure below

During the reflection of light, the frequency, speed, and wavelength do not change, but phase change may occur depending on the nature of the reflecting surface.

Associated terms of reflection

Reflecting surface: It is a surface on which light falls and bounces back.

Point of incidence: It is a point on the reflecting surface at which the incident ray strikes.

Normal: It is a perpendicular drawn on a reflecting surface at the point of incidence.

Incident ray: It is the ray of light that strikes the reflecting surface at the point of incidence.

Reflected ray: It is the ray of light that comes back into the same medium from the reflecting surface after reflection.

The angle of incidence: It is the angle between the incident ray and the normal.

The angle of reflection: It is the angle between the reflected ray and the normal.

Plane of incidence: It is a plane in which the incident ray and the normal are present.

Plane of reflection: It is a plane in which the reflected ray and the normal are present.

Glancing angle of incidence: It is the angle between the reflecting surface and the incident ray.

Glancing angle of reflection: It is the angle between the reflecting surface and the reflected ray.

Note: The sum of the angle of incidence and the glancing angle will be equal to 90 Degrees.

The angle of deviation for a plane reflecting surface

From the above figure, it is clear that

I+R+D=180

Therefore D=180-2I (since I=R)

Laws of Reflection

There are two laws of light reflection

The first law of reflection: Always the angle of incidence is equal to the angle of reflection

I=R

The second law of reflection: The incident ray, the reflected ray, and the normal, all lie in one plane.

Types of Reflection

Reflection of light can occur in two ways

1. Regular reflection: 

The reflection of light by a straight regular smooth surface is known as regular reflection. In this type of reflection, when a parallel beam is incident on the surface the reflected rays obtained also is a parallel beam.

2. Irregular reflection: 

The reflection of light by a rough irregular surface is known as irregular reflection. In this type of reflection, when a parallel beam is incident on the surface the reflected rays obtained will be in random directions (not parallel to each other).