Question

An object is placed 20 cm from a convex mirror. its image is formed 12 cm away from the mirror. find the focal length of the mirror.

Answer 1

Answer:

Refer to the attachment .

Explanation:

Answer 2

Answer:

The focal length of the mirror is 30cm.

Explanation:

From the mirror formula we have,

$\frac{1}{f} =\frac{1}{v} +\frac{1}{u}$          (1)

Where,

f=focal length of the mirror

v=image distance from the mirror

u=object distance from the mirror

From the question we have,

The object distance from the mirror(u)=-20cm

The image distance from the mirror(v)=12 cm

We get the following by inserting the variables in equation (1),

$\frac{1}{f} =\frac{1}{12} +\frac{1}{-20}$

$\frac{1}{f} =\frac{5-3}{60}$

$\frac{1}{f} =\frac{2}{60}$

$\frac{1}{f} =\frac{1}{30}$

$f=30cm$

Hence, the mirror's focal length is 30cm.

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