Light of Class 9
The reproduction of object formed by mirror or lens is called an image.
An image is formed when the light rays coming from an object actually meet (or appear to meet) at a point after reflection or refraction.
Images are of two types.
The image formed when two or more reflected or refracted rays intersect each other at a point in front of the reflecting surface (mirror) is known as a real image. It can be obtained on a screen.
e.g. The images formed on a cinema screen are real images.
The virtual image is formed due to apparent intersection of reflected or refracted light rays.
The image formed when two or more reflected or refracted rays appear to intersect at a point behind the normal. It can’t be obtained on a screen.
e.g. The image of our face in a plane mirror is a virtual image.
Ex.You have a height h. What is the minimum height possible for a plane mirror so that you can see your entire reflection in it without moving your head?
- Smaller than h but larger than h/2
- Smaller than h/2
- It depends on how far you stand from the mirror.
Solution: No matter how far you are from the mirror, the minimum heightnecessaryis h/2. The mirror has to be positioned just right, though.
TYPES OF MIRROR:
Spherical Mirror -
- Concave Mirror and
- Convex Mirror
Plane Mirror -
- Flat Mirror