Question

9 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location of image and magnification. Describe what happens to the image as the needle is moved farther from the mirror.

Answer 1

Given: A 4.5cm needle is placed 12cm away from a convex mirror of focal length 15cm.

To find the location of the image and the magnification.  

Solution:

According to the given criteria,

Object height, ho=4.5cm

Object distance, u=−12cm

Focal length of the mirror, f=15cm

Applying mirror formula, we get

f1=v1+u1⟹151=v1+−121⟹v1=151+121⟹v1=604+5⟹v=6.6cm

Hence, the image is at a distance of 6.6 cm,

Magnification, m=−uv=hiho⟹−−126.6=hi4.5⟹hi=6.64.5