Question

5. The focal length of a concave mirror is 10 cm.
Where should an object be kept in front of the
mirror so that its formed image be 5 times of the
object, while image be : (i) real (ii) virtual ? Also
find the position of image.
[Ans. Keeping object at a distance of 12 cm and
image is formed 60 cm, object will keep at a
distance of 8 cm in front of mirror and image will
formed at 40 cm]​

Answer 1

Answer:

Wehave mirror equation, begin mathsize 12px style 1 over v plus 1 over u equals 1 over f space........................ left parenthesis 1 right parenthesis

end style

where v is image to mirror distance to be calculated

u is object to nirror distance = 48 cm ; f is focal length of convex mirroe = -12 cm ( as per sign convention)

hence we can calculate v from eqn.(1) : begin mathsize 12px style 1 over v space equals space minus 1 over 12 plus 1 over 48 space equals space minus 1 over 16 end style or v = -16 cm

Hence image is formed at a distance 16 cm from mirror on the back side of mirror.