Question

An object is placed at 20cm in front of concave mirror of focal lens 10cm . calculate the position of image ?

Answer 1

ANSWER

Given : Object distance, u=−20 cm

A concave mirror forms a real magnified image only when the image to be formed is inverted i.e. m=−3

Magnification m=

u

−v

∴ −3=

−20

−v

⟹v=−60 cm

Using mirror formula :

v

1

+

u

1

=

f

1

∴

−60

1

+

−20

1

=

f

1

⟹ f=

4

−60

=−15 cm

Thus focal length of the mirror is 15 cm.

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Answer 2

Answer:

-20 cm

Explanation:

by using mirror formula

1/v+1/u= 1/f

1/v+1/-20 = 1/-10

v = - 20

..or simply if a object is kept at centre of curvature of concave mirror it's image is alsa formed at centre of curvature with same size but real and inverted

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