Basic Optical Devices Part 2 Lenses

Lenses Lenses are curved pieces of glass, plastic or crystal. There are two types of lenses: Diverging which have at least one Concave side: Have a virtual Focus Always create a smaller virtual image that is closer than the object… So they are used to correct nearsightedness Are used in telescopes as only as a part of a compound lens

Converging which have at least one Convex side: Used to gather light & into a real focus, Creates an erect virtual and larger image of an object placed closer than its focus the image is farther away than the object so they are used to correct farsightedness Create inverted real image Of an object placed farther away than the focus That get smaller the farther away the object is Converging lenses are often used in telescopes projectors, cameras etc.

Prisms Prisms are flat sided pieces of glass, plastic or crystal, They are used to: disperse white light into a spectrum. change the direction of a ray of light Diffraction Gratings Diffraction Gratings are a series of parallel slits usually in a plastic film. They use diffraction to disperse white light into a spectrum A Spectroscope is a devise that uses a prism or diffraction grating to study spectra