Question

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Answer 1

$\bigstar\huge\underline{\mathtt{ Solution :}}$

As per the given data ,

• object distance = - 20 cm

object distance is negative as distance is always measured from the pole of the mirror

• image distance = + 15 cm

Image distance is positive as distance is always measured from the pole of the mirror

We need to find the focal length of the mirror in order to do that simply use the mirror formula

➽ 1 / f = 1 / v + 1 / u

here ,

• f = focal length
• v = image distance
• u = object distance

Now let's substitute the given values in the above equation ,

➝ 1 / f = 1 / 15 - 1 / 20

➝ 1 / f = 4 - 3 / 60

➝ 1 / f = 1 / 60

➝ f = + 60 cm

This mirror is a convex mirror as the focal length of the convex mirror is always positive

The focal length of the mirror is + 60 cm