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JAMB Physics 2018 Paper

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Question : 80

Total: 87

The image of an object is located 6cm behind a convex mirror. If it's magnification is 0.6, calculate the focal length of the mirror

3.75cm
6.70cm
10.00cm
-15.00cm

Solution:

V = -6cm

M = 0.6cm

Recall m = $\frac{V}{U}$

U = $\frac{V}{M}$

U = $\frac{6}{0.6}$

U = 10

$\frac{1}{U}$ + $\frac{1}{V}$ = $\frac{1}{F}$

$\frac{1}{10}$ + $\frac{1}{-6}$ = $\frac{1}{F}$

$\frac{-4}{60}$ = $\frac{1}{F}$

F = $\frac{60}{-4}$

= -15cm

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