Question

An object is placed 40 cm in front of a convex mirror. The image appear 15 cm behind the mirror. What is the focal length of the mirror?​

Answer 1

Answer:

For convex mirror, given u = - 40 cm and v = 15 cm as per sign convention. f = 24 cm. Thus, the focal length of the mirror is 24 cm.

Explanation:

For convex mirror, given u = - 40 cm and v = 15 cm as per sign convention. f = 24 cm. Thus, the focal length of the mirror is 24 cm.

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Answer 2

Given: An object is placed 40 cm in front of a convex mirror. The image appear 15 cm behind the mirror.

To find: Focal length of the mirror

Explanation: Let the object distance be denoted by u, final velocity be v and focal length be f.

According to the sign convention, the distance in front of the mirror are taken to be negative and distance behind the mirror are taken to be negative.

u= -40 cm

v = 15 cm

Using mirror formula:

=>$\frac{1}{f} = \frac{1}{u} + \frac{1}{v}$

=>$\frac{1}{f} = \frac{1}{ - 40} + \frac{1}{15}$

=>$\frac{1}{f} = \frac{ - 3 + 8}{120}$

=>$\frac{1}{f} = \frac{5}{120}$

=>f= 24 cm

Therefore, the focal length of the mirror is +24 cm.