9th.Reflection of light...🎷

 Image formed by a convex mirror.

Virtual image :- As the reflected rays do not actually cross one another the image is called virtual.

The image formed by the convex mirror is always situated behind the mirror therefore virtual , smaller than the object , and erect.

One interesting fact about the convex mirror is that the nature of the image formed by a convex mirror does not depend on the distance of the object from the mirror.

Divergence of light :-

A convex mirror is also called a dispersing mirror because parallel rays get dispersed after reflection in this mirror.

Convergence of light :-

A concave mirror is also called a focusing mirror because parallel rays get focused after reflection in this mirror.

 Cartesian sign conventions

Some clues

1. According to the cartesians sign convention the pole P of the mirror is taken as origin (0).

2. Principle access is taken as X-axis.

🎺 The sign conventions are as follows...

1. The object is always kept on the left side of the mirror .

2. All distances parallel to the principal Axis are measured from the pole P.

3 A.The distances measured towards the right of the pole P are taken as positive (+ ve) .

B. The distances measured towards the left of the pole P are measured as negative (-ve).

4 A. Those distances measured above the principal axis vertically upward consider them positive (+ ve) .

B. Those distances are measured below the principle axis vertically downward considering them negative (- ve)

6. A. The focal length of a concave mirror is negative. 

B. Focal length of a convex mirror is positive + ve.

 Mirror formula

u - distance of object from the pole P .

v - distance of image from the pole P.

f - focal length

Magnification due to spherical mirrors.

h1 - height of the object.

h2 - height of the image.

m - magnification

One example

An object of height 7 cm is kept at a distance of 25 cm in front of a concave mirror. The focal length of the mirror is 15 cm. At what distance from the mirror should a screen be kept so as to get a clear image? what will be the size and nature of the image?

The minus sin is as sign convention.

So Screen kept at distance of 37.5 cm.

Height of the image is 10.5 cm.

Nature of image is 

a. Magnified , 

b. inverted , 

c. real.