Question

the focal length of a concave mirror is 10 cm find the position of image of the object placed at a distance of 20cm in front of the mirror​

Answer 1

Explanation:

Given:

Focal length of concave mirror, f = -20 cm

Distance of object from the mirror, u = -10 cm

use formula, 1/v + 1/u = 1/f

or, 1/v = 1/f - 1/u

or, 1/v = 1/-20 - 1/-10

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

or, v = +20cm

hence, image position is the 20cm right side from the pole of the concave mirror as shown in the diagram. The image is straight and bigger than the object.

Answer 2

Answer:

f= -20cm

U= -10cm

V=?

By using Mirror formula.

1/v + 1/u = 1/f

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

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

L.C.M.=2×10=20

1/v=1/20

V=20cm

*Image is formed behind the mirror.*

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