Question

An object of size 7cm is placed at 27 cm in front of a concave mirror of focal length
18cm. At what distance the screen should be placed from the mirror so that a sharp
image can be obtained?.Find the size and nature of the image.​

Answer 1

Answer:

An object of size 7cm is placed at 27 cm in front of a concave mirror of focal length

18cm. At what distance the screen should be placed from the mirror so that a sharp

image can be obtained?.Find the size and nature of the image.

Explanation:

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Answer 2

Answer:

At the distance of 54cm we would obtain the sharp image . The size of the image would be 14 cm and it would be real and inverted

Explanation:

Given in the question:

size of the object :h = 7cm,

distance from mirror : u = -27cm,

and the focal length: f = -18cm

we have to find v (distance from mirror to obtain sharp image)

and h' (size) and nature of the image

Solution–

We know that,

1/v + 1/u = 1/f

therefore, 1/v + 1/-27 = 1/-18

therefore, 1/v = 1/-18 + 1/27

, 1/v = -1/54

therefore, v = 54cm ( distance from the object at which

sharp image is obtained )

To find the height of the image or h' —

We know that, m= h'/h = -v/u,

therefore, h'/7 = - (-54/-27)

; h'/7 = -2

; h' = -14cm

As the height came is negative , therefore, the image

formed must be real and inverted.

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