Question

A 2 cm tall object is placed 30cm in front of a concave mirror with focal length of 25 cm. What is the height of the image?

Answer 1

Answer:

$- 10$ cm

Explanation:

$h_{o}$ = height of the object = 2 cm

$h_{i}$ = height of the image

$d_{o}$  = distance of the object from the mirror = 30 cm  

$f$  = focal length of the mirror = 25 cm  

$d_{i}$  = image distance

using the mirror equation

$\frac{1}{d_{o}} + \frac{1}{d_{i}} = \frac{1}{f}$

$\frac{1}{30} + \frac{1}{d_{i}} = \frac{1}{25}$

$d_{i} = 150$ cm

using the equation

$\frac{h_{i}}{h_{o}} = \frac{- d_{i}}{d_{o}}$

$\frac{h_{i}}{2} = \frac{- 150}{30}$

$h_{i} = - 10$ cm