Question

If an object placed in front of a concave mirror at the distance of 10cm from it's pole.Calculate the image distance,if the focal length of this mirror is 10cm.​

Answer 1

Answer: 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:

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

Explanation:

therefore by using the formula, image position is 20cm