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WAEC Physics 2015 Paper

Question : 32

Total: 50

Solution:

Concept:

For a concave mirror, the mirror formula and magnification formula relate the object distance, image distance, and focal length.

Explanation:

Using the mirror formula:

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

Given,

u = 20 \, \text{cm}

and

f = 15 \, \text{cm}

(positive for a concave mirror).

Substitute the values:

\frac{1}{v} = \frac{1}{f} - \frac{1}{u} = \frac{1}{15} - \frac{1}{20}

\frac{1}{v} = \frac{4 - 3}{60} = \frac{1}{60}

Therefore,

v = 60 \, \text{cm}

Linear magnification is given by:

M = \frac{v}{u} = \frac{60}{20} = 3.0

Answer:

The linear magnification of the image formed is

3.0

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