Light

Reflection&

Refraction

Reflection

When light falls on a highly

polished surface like a mirror

most of the light is sent back

into the same medium. This

process is called reflection of

light.

Laws of Reflectioni) The angle of incidence is equal to angle of reflection.

ii) The incident ray, the normal and the reflected ray lie on the same plane.

Plane MirrorImage formed by plane mirror is

always erect and virtual. The size of

image is equal to the size of object.

The image formed is far behind the

mirror as the object in front of it.

The image is also laterally inverted.

Spherical Mirrors Spherical mirror is a curved mirror which is a part of a hollow sphere. Spherical mirrors are of two types. They are concave mirror and convex mirror.

SPHERICALMIRROR

CONCAVE CONVEX

A spherical mirror whose reflecting

surface is curved inwards is a concave

mirror. It is also known as converging mirror.

CONCAVE MIRROR

A spherical mirror whose reflecting

surface is curved outwards is called convex mirror. It is

also known as diverging mirror.

Convex Mirror

Refraction

When light travels obliquely

from one transparent medium

into another it gets bent. This

bending of light is called

refraction of light.

Laws of Refraction

i) The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane.

ii) The ratio of sine of angle of incidence to the sine of angle of refraction is a constant. This law is also called Snell’s law.

Refractive IndexThe absolute refractive index of a medium is the ratio of the speed of light in air or vacuum to the speed of light in medium.

Refractive Index Of Some MediaMEDIUM INDEX

Air 1

Water 1.33

Ice 1.31

Alcohol 1.36

Spherical LensesA spherical lens is a transparent material bounded by two surfaces one or both of which are spherical.

SphericalLens

CONCAVE CONVEX

Convex lensConvex lens is thicker in the middle and thinner at the edges. Rays of light parallel to the principal axis after refraction through a convex lens meet at a point (converge) on the principal axis.

Concave lens Concave lens is thinner in the middle and thicker at the edges. Rays of light parallel to the principal axis after refraction get diverged and appear to come from a point on the principal axis on the same side of the lens.

Images Formed By Convex Lens

Object position

Image position Image size Nature of image

At Infinity At F2 Diminished Real & Inverted

Behind 2F1 B/W F2 &2f2 Small Real & Inverted

At 2f1 At 2F2 Same Real & Inverted

Between F And 2F

Beyond 2F2 Magnified Real & Inverted

At F1 At Infinity Highly Magnified

Real & Inverted

B/W The Pole (P) And F1

Same Side Of Lens

Magnified Virtual And Erect

Images Formed By Concave Lens

Object position

Image position

Image size Nature of image

At Infinity At F1 Diminished Virtual And Erect

B/W O & Infinity

Between O And F1

Small Virtual And Erect

Made by:

ClassX-C

Sakshi Gupta