A convex lens of focal length 50cm produces a virtual image of magnification 2. How far should
the object be moved so that a real image of the same magnification is produced?
Answers
Explanation:
The focal length of a convex lens is 50 cm. To obtain a real image of double the size how far does the object have to be kept from the lens?
The lens formula is 1v−1u=1f, where v,u and f are the distance of the image from the lens, the distance of the object from the lens and the focal length respectively.
As per the new Cartesian convention, distances from the lens toward the side of the object are negative and distances toward the other side are positive. Distances above the principal axis are positive and distances below the principal axis are negative.
The magnification is, M=vu.
For a real image the magnification is negative and for a virtual image it is positive.
It is given that the image is real and that the image is double the size of the object.
⇒M=vu=−2⇒v=−2u.
It is also given that the focal length, f=50.
1v−1u=1f⇒1−2u−1u=150.
⇒−32u=150⇒u=−50×32=−75.
⇒ The object has to be kept at a distance of 75 cm from the lens.
Answer:
Your question solution. I an glad to help you.
