10 grade science> A converging beam of rays is incident on ...

A converging beam of rays is incident on a diverging lens.Having passed through the lens the rays intersect at a point 15cm from the lens on the opposite side.If the lens is removed the point where the rays will meet will move 5cm closer to the lens.The focal length of the lens is ?

SUDHARSANA V V , 7 Years ago

Grade 10

2 Answers

Arun

Last Activity: 7 Years ago

Dear student

Given,
Image distance, v=15 cm
Object distance, u=15-5=10 cm (It is the distance when lens is removed. i.e object distance)
Now,
Using formula,
1/v-1/u=1/f
or 1/f=1/15 -1/10
or f=-30 cm

Regards

Arun (askIITians forum expert)

Approved

Rishi Sharma

Last Activity: 4 Years ago

Dear Student,
Please find below the solution to your problem.

Given,
Image distance, v=15 cm
Object distance, u=15-5=10 cm
(It is the distance when lens is removed. i.e object distance)
Now, Using formula,
1/v-1/u=1/f
or
1/f=1/15 -1/10
or
f=-30 cm

Thanks and Regards