Question

61. The image of an object formed by a convex lens is of the same size as that of the object, if the
image is formed at a distance of 50 cm from the lens at what distance from the lens is the object
placed? find the focal length and the power of the lens used.
u=-25, f=25, P=2D
u=-50, 1=25, P-4D
u--50, 8-20, P=4D
u=-50, f=25, P=2D​

Answer 1

Answer:

u=-50

f=25

p=4d

Explanation:

p=100/g

and

f=r/3

innthis case r=50

Answer 2

Answer:

Explanation:

Same size of image is formed by a convex lens only when the object is placed at a distance u=2f from the optical center and image is also formed at distance 2f on other side of lens.

⟹2f=50

⟹f=25cm

P=  

f(m)

1

​  

=  

0.25

1

​  

 

⟹P=+4D