A person has a normal near point $$25 \mathrm{~cm}$$. What is the magnifying power of the simple microscope he used, if the focal length of the convex lens used is $$10 \mathrm{~cm}$$ and the final image is formed at the least distance of distinct vision?

A lens of power $$+1 \mathrm{D}$$ is made in contact with another lens of power $$-2 \mathrm{D}$$ the combination will then act as a:

What will be change in wave length, if a light of wave length $$600 \mathrm{~nm}$$ travels from air enters a medium of refractive index 1.5 and continues its journey through that medium?

A point object is placed on the optic axis of a convex lens of focal length $$f$$ at a distance of $$2f$$ to the left of it. The diameter of the lens is $$d$$. An eye is placed at a distance of $$3f$$ to the right of the lens and a distance $$h$$ below the optic axis. The maximum value of $$h$$ to see the image is