A point object moves along the principal axis of a convex lens of focal length f , such that its image, also formed on the principal axis at a distance 
f (at t = 0) moves away from the lens with a uniform velocity α . Find the velocity of the point source as a function of time t .
Text Solution
Verified by ExpertsCHECK THE SOLUTION.
Sol. Applying the equation for image formation by a lens, we get
– 
= 
– 
= 
… (1)
u = – 4f
The position of the image is given by
f = 
f + α t, at time t … (2)
∴ The corresponding position of the object is given by (at time t)
– 
= 
or 
= 
– 
On differentiating the equation w.r.t. time, we get
– 
= – 
or 
= 
= 
( α ) … (3)
Velocity of the source = 
= 
α … (4)
Prepare Smarter with CGP Edu
Get practice questions, solutions, and test series in one place.
Write a Review
Share your experience with this question and solution.
Commentary
Send your comment, doubt, correction, or feedback to admin.
Similar Questions
Explore conceptually related problems