Spherical mirrors

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Slide 10

Some definitions of convex and concave mirrors

5.Aperture of the mirror :

The portion of the hollow spherical surface from which the mirror reflections take place is called the aperture of the mirror.

In the figure 2, the distance MM’ is the aperture of the mirror.

Slide 11

Some definitions of convex and concave mirrors

6.Focal Length of a mirror :

When parallel rays of light coming from an infinite distance, fall on either a concave or a convex mirror, they are reflected back to a point on the principal axis XY.

The focus is where the image is formed of an object placed at a far distance.

Slide 12

Focal length of a concave mirror

In a concave mirror, the rays appear to converge at a point F. The distance PF is called the focal length and F is called the focal point.

The focus is in front of the mirror.

Slide 13

Focal length of a concave mirror :-

In case of convex mirrors, the parallel rays, on reflection, appear to diverge from a point F.

This point again is called the focal point of the convex mirrors and the distance PF is called the focal length.

The focus, in this case is behind the mirror

Slide 14

Real and Virtual images

1. In a concave mirror, the focus is real.

The object and the image lie on the same side of the

mirrored surface. A real image is called so because it

can be caught on a screen.

2. In a convex mirror, on the other hand, the object and

its image lie on the opposite sides of the mirrored

surface. The image therefore is a virtual image.

It cannot be captured on a screen.

3. In a plane mirror, the image again is a virtual one, as

it does not form on the same side as that of the

object.