Question

frds please define the formula for mirror reflection of light at curved surfaces fast

Answer 1

1/f= 1/u + 1/v.

This equation is referred to as the mirror formula. The formula holds for both concave and convex mirrors.

When applying the mirror formula, it is necessary to observe the following points:

That all distances are measured from the mirror as the origin.

All real distances are positive while all virtual distances are negative.

A concave mirror has a positive focal length while a convex mirror has a negative focal length.

Example 

1)Determine the position, size and nature of the image of an object 4cm tall placed on the principal axis of a concave mirror of focal length 15cm at a distance 30cm from the mirror.

solution 
u=30cm, f= 15cm, ho=4cm

1/v=1/f-1/u

= 1/15 – 1/30 =1/30

v =30cm

Also, m=v/u =hi/ho

Thus, hi=(30cm x 4cm)/30cm =4cm.

Thus the image formed is real and same size as the object.

2. A convex mirror of focal length 9cm produces an image on its axis 6cm from the mirror. Determine the position of the object.

solution

f= -9cm, v= -6cm.

1/u = 1/f – 1/v = -1/9 – (-1/6)

1/u= (-2+3)/ 18 =1/18

u=18cm