Question

A 10.00 CM tall light bulb is placed at a distance of 90.0 CM from a concave mirror

having a focal length of 21 CM Determine the image distance and the image size

Answer 1

Write the equation for a concave mirror:

$$\dfrac 1f=\dfrac 1o+\dfrac 1i,\\\space\\ i=\dfrac{of}{o-f}=\dfrac{(-90)(-21)}{(-90)-(-21)}=-27.4\text{ cm}.\\\space\\ h_i=-h_o\dfrac{i}{o}=-10\dfrac{-27.4}{-90}=-3\text{ cm}.$$