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An object 1 cm high is placed at a distance of 1.5 m from the screen. How far a concave mirror be placed so that it may form a 2cm high image of the object on the screen? Also find the focal length of the mirror.

An object 1 cm high is placed at a distance of 1.5 m from the screen. How far a concave mirror be placed so that it may form a 2cm high image of the object on the screen? Also find the focal length of the mirror.

Grade:11

1 Answers

vikas askiitian expert
509 Points
13 years ago

since image is larger than object so its image is virtual ...

let the mirror is placed at u distance far from object & v distance far from screen...     (mirror is bw object & screen)

v/u = 2/1 = 2

v = 2u                   (given)

v + u = 1.5           

u = 1.5/3 = -50cm

v = 100

focal length = f

applying lens formula

1/v + 1/u =1/f

-1/50 + 1/100 = 1/f

f = -100cm

thus mirror should be placed at a distance 100cm from screen...

approve my ans if u like it

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