# Light

Image

## Light

Light is an electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight.

Light

## Reflection

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

Reflection

## Reflection of Light

When the light rays are incident on a reflecting surface, they get reflected in the same medium.

Reflection of Light

## Refraction of Light

Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon.

Refraction of Light

## Diffraction of Light

Diffraction refers to various phenomena which occur when a wave encounters an obstacle. Diffraction phenomenon is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings.

Diffraction of Light

## Law of Reflection

(i)The angle of incidence is equal to the angle of reflection, and (ii) The incident ray, the normal to the mirror at the point of incidence and the reflected ray, all lie in the same plane.

Law of Reflection

## Spherical Mirror

Spherical mirror is the most commonly used type of curved mirror. The mirrors whose reflecting surfaces are spherical are known as spherical mirrors.

Spherical Mirror

## Concave Mirror

A spherical mirror, whose reflecting surface is curved inwards, that is, faces towards the center of the sphere, is called a concave mirror.

Concave Mirror

## Convex Mirror

A spherical mirror, whose reflecting surface is curved outwards, is called a convex mirror.

Convex Mirror

## Aperture

The reflecting surface of a spherical mirror is by and large spherical. The surface, then, has a circular outline. The diameter of the reflecting surface of spherical mirror is called its aperture.

Aperture

## Magnification

Magnification produced by a spherical mirror gives the relative extent to which the image of an object is magnified with respect to the object size.

Magnification

## Formula for Calculating Magnification

It is expressed as the ratio of the height of the image to the height of the object. It is usually represented by the letter m.

Formula for Calculating Magnification

## Snell's Law of Refraction

Snell's law is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water and glass.

Snell's Law of Refraction

## Statement and Equation of Snell’s Law

Snell's law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of phase velocities in the two media, or equivalent to the opposite ratio of the indices of refraction.

Statement and Equation of Snell’s Law

## Refractive Index

If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction; i.e., n = sin i / sin r.

Refractive Index

## Lens

A transparent material bound by two surfaces, of which one or both surfaces are spherical, forms a lens.

Lens

## Converging Lens

A lens may have two spherical surfaces, bulging outwards. Such a lens is called a double convex lens. It is thicker at the middle as compared to the edges. Convex lens converges light rays hence they are called converging lenses.

Converging Lens

## Diverging Lens

A double concave lens is bounded by two spherical surfaces, curved inwards. It is thicker at the edges than at the middle. Such lenses diverge light rays hence such lenses are called diverging lenses.

Diverging Lens

## Converging and Diverging Lenses

The slide above shows both converging as well as diverging lenses.

Converging and Diverging Lenses

## Power of Lens

The degree of convergence or divergence of light rays achieved by a lens is expressed in terms of its power. The power of a lens is defined as the reciprocal of its focal length.

Power of Lens
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