Question

A concave mirror forms a real image which is twice the size ofthe object. If the object is located 20 cm from the mirror, theradius os curvature must be about: a.) 13 cm b.) 20 cm c.) 27 cm d.) 40 cm

Answer 1

Answer: 40cm

v= Distance of object from mirror

u= Distance of image from mirror

hi= height of image

ho= height of object

f= focal length.

Answer 2

Answer:

27cm

Explanation:

object distance =u=20cm

the image formed is real then magnification will always be negative

m= -v/u

so

according to the condition based on the problem ,we get,

v=2u,

therefore,by putting values in we get,

v=40cm

then we get the object distance and image distance that is20cm and 40 cm

by mirror formula we get,

1/f=1/v+1/u

1/f=1/20+1/40 therefore,

1/f=3/40

then,

f=40/3 cm

and then by the formula we get the radius of curvature,

f=r/2

40/3 multiplied by 2

we get

=80/3=26.666666............

then we get radius of curvature nearly about,27 cm

therefore the answer is 27 cm