Reflection of light, image and spherical mirrors

Reflection of light

Reflection of light :-

It is the change in direction of a light at an interface between two different media so that the light returns into the medium from which it originated.

Laws of reflection of light :-

When a ray of light is reflected from a smooth surface then

  1. The angle of reflection is equal to the angle of incidence.
  2. The incidence ray, the reflected ray and the normal to the surface at the point of incidence all lie in the same plane.
reflection of light
Fig . 1 . Ray diagram for Reflection of light through a Plane Mirror .

These laws are valid at each point on any refleflecting surface whether plane or curved.

Image :-

An imase may be defined as that point where the light rays coming from an object meet or appears to meet after reflection or refraction.

Types of image :-

There are of two types.

1.Real image ;- A real image is that image which is formed when the light rays coming from an object actually meet each other after reflection or refraction.

  • A real image can be obtained on the screen. The real image is always inverted.

Example – image formed on cinema screen.

2. Virtual image :- A virtual image is that image which is formed when the light rays coming from an object do not actually meet , but appear to meet when produced backward.

  • A virtual image can not be obtained on screen. The virtual image is always erect.

Example – image formed in the mirror, when we stand in front of that mitror.

Spherical mirrors :-

It is the mirror which has the shape of a piece cut out of a spherical surface.

CNX UPhysics 35 02 ConvexCave 1
Fig . 2 . Spherical Mirrors .
  • There are two types of spberical mirrors –
  1. Concave mirror :- A concave mirror is a mirror with a curved reflecting surface which is curved inwards.

It is also known as converging mirror as this reflecting surface collects light incident on its surface and reflects the parallel rays of light towards the common focus (F).

2. Convex mirror :- A convex mirror or diverging mirror is a curved mirror in which the reflective surface bulges towards the light source.

Convex mirror reflect light outwards, therefore they are not used to focus light. The image is smaller than the object but gets larger as the object approaches the mirror.

Position and characteristics of Image formed by Spberical mirror with Ray diagram :-

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Fig . 2 . Ray diagram for convex mirror .
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Fig . 3 . Ray diagram for Concave Mirrors .

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