Reflection | types of reflection | laws of reflection | types of image | real image | virtual image

BASICS OF RAY OPTICS by "advguruji"

Reflection -

The bouncing back of light is called reflection. It is of two types:

Regular reflection and diffused reflection.

Regular reflection -

when parallel rays of light incident on a smooth reflecting surface and again go parallel to each other after reflection, this type of reflection is called regular reflection.

Regular reflection

Diffused reflection -

when parallel rays of light incident on a rough reflecting surface and the rays do not go parallel to each other after reflection this type of reflection is called diffused reflection.

Diffused reflection

Laws of reflection :-

1. The angle of incidence is equal to the angle of reflection.

2. The incident ray, reflected ray and the normal all lie on a same plane.

In simple words, reflection is the process of obtaining an image of an object, and there are two types of objects.

1. Luminous objects :

Those objects which emit their own light are called luminous objects.

Example : Sun, stars, etc.

2. Non luminous objects :

Those objects which reflect the light coming from a luminous object and do not emit their own light are called non luminous objects.

Example : toys, plants, etc.

Now, some concepts about image.

Image -

It is an optical appearance of an object when light rays coming from an object reflect from a reflecting surface and intersect each other.

Or,

when two or more light rays intersect each other at a point after reflection(or refraction), an image is formed.

It is of two types:

Real image and virtual image

Properties of a real image :-

1. It can be obtained on a screen.

2. It is always inverted.

3. It is always formed in front of the reflecting surface.

4. It is formed by the actual intersection of light rays.

5. It is shown by a continuous line.

6. Magnification of a real image is negative. (because height of object and height of image are opposite in direction)

Real image by concave mirror
when object is between C and F

Example : image formed on a movie theatre screen.

Properties of a virtual image :-

1. It cannot be obtained on a screen.

2. It is always erect.

3. It is always formed behind the reflecting surface.

4. It is formed when light rays do not actually intersect each other but intersect virtually when produced behind the reflecting surface.

5. It is shown by a dotted line.

6. Magnification of virtual image is positive. (because height of object and height of image have same direction)

Example : image formed by a plane mirror (grooming mirror).