Question

The distance between object and screen is 20 cm. What type of mirror and what focal length of the mirror will provide image magnified three times on the screen?
Also please write the steps of how you got the answer.

Answer 1

Explanation:

Given

Magnification , m=3

Object distance, u =20cm

USING MAGNIFICATION FORMULA

m= -V/20

V= 60 cm

Distance of the image from the mirror is 60

USING MIRROR FORMULA

1/f = 1/v +1/u

1/f = 1/-60 + 1/-20

F = 15 cm

the focal length of the mirror is - 15

TO find the distance of the object from the mirror

using magnification Formula

m = h ( height of images ) /h ( height of object )

m= v/u

as per question ' there times the height of the object '

v = 3u

using mirror formula

1/-3u+ 1/u 1/-15

u = 10 cm .

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