Question

A 10.00cm.tall light bulb is placed at a distance of 90.0cm from a concave mirror having a focal length of 21cm determine the image distance and the image size.

Answer 1

The image distance:

$$i=\frac{of}{o-f}=\frac{90·21}{90-21}=27.4\text{ cm}.$$

The size:

$$H_i=H_o\frac{i}{o}=3.04\text{ cm}.$$