Question

A convex mirror has a focal length of ?35 cm. Where is the image if the image is upright and three-fourths the size of the object?

Answer 1

We know that from the convex mirror

                                      M =hi/ho =-di/do =(3/4)ho/ho =-di/do

Then (3/4) =-di/do====>do=(4/3)di

In the case of the image height, a positive value indicates an upright image.

given that focal length is f = 35cm

Now image distance is given by 1/f =1/do+1/di =(1/4di/3)+1/di

                                                  1/-35 =1/di[-3+4/4] ==>1/35 =7/4di then di = -61.25cm

The negative values for image distance indicate that the image is located behind the mirror