Question

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

Answer 1

Answer:

The answer will be 40 cm

Explanation:

According to the problem curvature of the  mirror is ,f = 40 cm

For regular  image

let u=u1,  v=−2u,  f=20cm

Now we know, 1/v+1/u=1/f

=>1/−2u −1/u1   =  −1/40

=> u1 = 60cm

Now it is stated that the image produces will doubled from the actual size

For this,

let  u=−u2   ,    v=2u2    f=−40cm

Similarly we can say  u2=20cm

Therefore the distance between two position of object are

u1−u2  =  60−20=40cm