Question
An illuminated object and a screen are placed 90 cm apart. What is the focal length and nature of the lens required to produce a clear image on the screen, twice the size of the object?
Solution
Given, the object and the screen are placed 90 cm apart.
As the image is real, the lens must be a convex lens and it should be placed between the object and the screen.
Let the distance between object and convex lens = x, then
Now,
Now, using the lens formula,
As the image is real, the lens must be a convex lens and it should be placed between the object and the screen.
Let the distance between object and convex lens = x, then
Now,
Now, using the lens formula,
