Question

OR
A 4 cm object is placed 20 cm before the concave mirror. Its focal length is 15cm.
i) Find the image distance.
ii) what is its magnification?
iii) what is the height of the image formed
Also draw the ray diagram for this situation
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Answer 1

Answer:

Image distance = 60 cm in front of the mirror

Magnification = -3 (enlarged image)

Height of the image = 12cm (real and inverted)

Explanation:

Given,

• object height = h = 4cm
• object height = h = 4cmobject distance = u = -20cm
• object height = h = 4cmobject distance = u = -20cmfocal length= f = -15cm

We know,

1/u+1/v=1/f

or 1/(-20)+1/v=1/(-15)

or 1/v = 1/(-15) - 1/(-20)

or. 1/v = (-20+15)/(15*20)

or 1/v = -1/60

or. v = -60cm

Therefore, m = -v/u = -(-60)/-20 = -3

m = h'/h

or -3 = h'/4

or h' = (-3)*4 = -12cm

Therefore,

Image distance = 60 cm in front of the mirror

Magnification = -3 (enlarged image)

Height of the image = 12cm (real and inverted)