Basic Optical Devices

1. Basic Optical Devices Part 2 Lenses

2. 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

3. 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.

4. 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