L i g h t

Acknowledgement

• Information and pictorial illustrations to create this

work have been drawn from class notes, prescribed

text books and various internet resources. The

author gratefully acknowledges the same. Any

objections to the use of internet resources may

please be indicated to suddurocks@yahoo.in so that the

same can be removed from the illustrations used in

this file.

• This presentation is created with the sole intention

of benefitting a large number of student community.

This may not be used for any commercial purpose.

Contents :

Light

Laws of Reflection

Regular & Diffused Reflection

Luminous & Non – Luminous Objects

Real & Virtual Images

Power of Accommodation

Least Distance of Distinct Vision

Short – Sightedness

Long – Sightedness

Persistence of Vision

Perception of Colour

Fascinating Facts

Some Interesting Pictures

Light

Light is a form of energy.

Light travels in a straight line.

Light enables us to see the objects

around us.

The light reflected from objects falls into

our eyes & thus, we can see the

objects.

Dispersion of light is splitting of white or

some other light into its components.

Laws of Reflection

The light ray which strikes any surface

is called the Incident Ray.

The ray that comes back from the

surface after reflection is known as the

Reflected Ray.

The perpendicular to the surface at the

point of incidence is known as Normal.

• The angle between the normal

and incident ray is called the

Angle of Incidence.

• The angle between the normal

and the reflected ray is known

as the Angle of Reflection.

• The angle of incidence is

always equal to the angle of

reflection.

• This is known as the Law of

Reflection.

Regular & Diffused Reflection

Reflection from a smooth surface

like that of a mirror is called

Regular Reflection.

When all the parallel rays reflected

from a plane surface are not

parallel, the reflection is known as

Diffused or Irregular reflection.

Luminous & Non – Luminous Objects

• Those objects which emit their own

light are called Luminous Objects.

• The objects which do not emit light of

their own, but they reflect light falling

on them, are called Non – Luminous Objects.

Real & Virtual Images

The image formed when incident rays

after reflection actually meet at a

point is known as a Real Image.

The image formed when incident ray

after reflection do not actually meet,

but appear to meet at a point is

knows as a Virtual Image.

Power of Accommodation

The ability of the eye to focus the

distant objects as well as the

nearby objects at the retina by

changing the focal length or

converging power of its lens is

known as the Power of

Accommodation.

Least Distance of Distinct Vision

The minimum distance at which an

object must be placed so that a

normal eye may see the object

clearly without any strain on the eye

is known as the Least Distance of

Distinct Vision.

It is about 25cm for a normal eye.

Short – Sightedness

Myopia or Short Sightednessmeans a person can see only nearby objects clearly, but cannot see distant objects.

This defect is removed by using a concave lens.

Long – Sightedness

Hypermetropia or Long –Sightedness is the reverse of Myopia.

A person suffering from this defect can see distant objects clearly, but not nearby objects.

The defect is removed by using convex lens.

Persistence of Vision

Impression of an image on the retina lasts for 0.1 sec after the removal of the object.

This effect is known as Persistence of Vision.

Perception of Colour

The human eye contains a large number of cell rods and cones which are sensitive to light.

The rods respond to the intensity of light and the cones respond to the colour of the light.

If cone cells are absent in the eye, then such a person is Colour Blind.

Fascinating Facts

A ray of light is an idealisation.

In reality, we have a narrow

beam of light which is made

up of several rays.

For simplicity, we use the term

ray for a narrow beam of light.

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Thank You !!!

Compiled By :

Sudarshan . S . K .

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