Question

object placed infornt of a concave mirror at a distance of 25cm I) what is distance of image if focal length is 15cm II) what is the focal length if the image distance is 9.37cm
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Answer 1

Answer:

no 1

CONCEPT:

Concave mirror: The mirror in which the rays converge after falling on it is known as the concave mirror.

Concave mirrors are also known as a converging mirror.

The focal length of a concave mirror is negative according to the sign convention.

Mirror Formula: The following formula is known as the mirror formula:

where,

f = focal length 

v = the distance of the image from the mirror,

u = the distance of the object from the mirror.

CALCULATION:

Given that,

Object distance, u = -25 cm,

Focal length, f = -15 cm

By using mirror formula:

⇒ 

⇒ Image distance (v) = -10 / 375  = - 37.5 cm. So option 4 is correct.

NOTE: 

The lens formula is applicable to both the concave and convex lens.

And for all lens object distance is considered as positive

The sign convention used for the focal length of a concave lens is considered as negative, whereas for the convex lens it's considered as positive

No 2 Answer I can't give because I don't know the answer