Question

A concave mirror of curvature 40cm used for for shaving purpose produce image of of double size as that of the object object distance must be

Answer 1

Answer:

30cm

Explanation:

the image is 4 times the object thus,

(-v/u) =4

u=(-v) /4

now using the mirror formula

also here f=(-40) (focal length of concave mirror is negative)

1/f=1/v +1/u

1/(-40)=1/v + (-4)/v

1/(-40)= (-3)/v

v=3*40=120

u= (-120/4)=(-30)

u= (-30)cm

thus the object is 30 cm away in front of mirror