Question

A glowing electric light bulb placed 15 cm from a concave spherical mirror produces a real image 8.9 from the mirror. the light bulb is moved to a position 20cm from the mirror
a) what is the image position? (answer with -1000 if the image does not exist)

Answer 1

Answer:

The image will form at distance d = 7.75 cm from the mirror

Explanation:

As we know that the bulb is placed at 15 cm distance from the concave mirror

Then the image will form at distance d = 8.9 cm

now we have

$\frac{1}{d_i} + \frac{1}{d_0} = \frac{1}{f}$

so we have

$\frac{1}{8.9} + \frac{1}{15} = \frac{1}{f}$

$f = 5.58 cm$

Now when bulb is placed at distance 20 cm from the mirror

then again we have

$\frac{1}{d_i} + \frac{1}{d_0} = \frac{1}{f}$

$\frac{1}{d_i} + \frac{1}{20} = \frac{1}{5.58}$

now we have

$d_i = 7.75 cm$