Question

1. A concave mirror has a radius of curvature of 15 cm. if an object 1 cm high is put 20 cm in front of the mirror, where will the image be formed? What is the height of the image?

Answer 1

Answer:

Given,

h’=5 cms

u(object distance)= -15 cms

Radius of curvature=20 cms ,then focal length is half of it i.e 10 cms.Also,focal length of a concave mirror is always neagtive.

Solving procedure is given below:

→1/f =1/v +1/u

→1/-10 = 1/v + 1/-15

→1/-10 + 1/15 = 1/v

→LCM would be 30.The numerator would be -3+2 i.e -1.The denominator would be 30 cms.

→1/v= -1/30.On reciprocating both sides,we get v= -30 cms.

Also, Magnification of mirror is -v/u.

→-30/15= -2 times.Here,negative sign signifies that image is real and inverted.

→Further,M=h'/ho(where h' is image size and ho is object size)

→2=h'/5 cm .i.e h'=10

Explanation: