Question

A 5.0 cm tall light bulb has placed a distance of 50 cm from a convex mirror having a focal length of 10 cm. What is the image height?

• A. 6/5 cm
• B. -6/5 cm
• C. -5/6 cm
• D. 5/6 cm

Answer 1

The correct option is D

5/6 cm

By using mirrors formula,

$\frac{1}{u}$ + $\frac{1}{v}$ = $\frac{1}{f}$ , or

$\frac{1}{(-50)}$ + $\frac{1}{v}$ = $\frac{1}{10}$ (u is negative as it is towards left of optical centre)

$\frac{1}{v}$ = $\frac{1}{10}$ + $\frac{1}{50}$

$\frac{1}{v}$ = $\frac{(5+1)}{50}$

Therefore, v = $\frac{50}{6}$ cm

Now, $\frac{-v}{u}$ = $\frac{heightofimage}{heightofobject}$

$\frac{\frac{-50}{6}}{-50}$ = $\frac{heightofimage}{5}$

Therefore, height of image = $\frac{5}{6}$ cm