A concave lens is used to diverge incident rays. This helps to create a virtual image on the opposite side of the refracting surface.
It can collect and focus the light then we can see the objectives easily and clearly.
Optical filter is made by glass.after the coating desginer design the curve.then coating in the oven.
An optical filter used in a microscope can make the observe more bright.
The optical filter is made of glass. After the coating designer design the curve. Then coating in the oven.