In the figure shown here, what is the equivalent focal length of the combination of lenses (Assume that all layers are thin) ?
Two thin lenses are of same focal lengths $$(f)$$, but one is convex and the other one is concave. When they are placed in contact with each other, the equivalent focal length of the combination will be :
During a cloudy day, a primary and a secondary rainbow may be created, then the :
If the screen is moved away from the plane of the slits in a Young's double slit experiment, then the :