Physics, asked by seema25, 1 year ago

How far should an object be placed from the pole of a converging mirror of focal length 20 cm to form a real image of the size exactly 1/4 th the size of the object.

Answers

Answered by Davinder123
18
. be from the pole of a concave mirror of focal length 20 cm to form an real image . ... Focal length of concave mirror,f = – 20cm ( – ive for concave mirror) ... of image to size of object which is equal to ratio of image distance to object distance) ... 1/20 = 1/u + 5/u as image is real so v will be negative so on putting its value it ...
Answered by anthonypaulvilly
4

Answer:

   u = -100cm

Explanation:

focal length (f) = -20cm

Magnification (M) = 1 / 4

image distance (v) = v

object distance (u) = u

M = -v / u

Here magnification is negative because it forms a real image

This is because virtual image formed by concave mirror is enlarged whereas according to the question the image is diminished and hence it forms a real image

-(1 / 4) = -v / u

1 / 4 = v / u

u = 4v -------{i}

1 / v + 1 / u = 1 / f

1 / v + 1 / 4v = - 1 / 20

4 / 4v + 1 / 4v = -1 / 20

5 / 4v = -1 / 20

4v = -100

v = -25cm

u = 4v = -100cm

∴ The object should be placed 100 cm to the left of the mirror.

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