Mirrors, Prisms, Diffraction Gratings and Spectroscopes And Lenses Basic Optical Devices Mirrors, Prisms, Diffraction Gratings and Spectroscopes And Lenses

Basic Optical Devices are used to… Change the Direction of a Ray of Light Gather parallel rays of light and focus them at the Focus or Focal Point This focus can be… Real, that is the light rays really meet there or Virtual that is the rays only appear to meet there Disperse white light into a spectrum Create an Image which is… Real and can be Projected onto a screen (its really there) Virtual which cannot be projected (it just appears to be there!)

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

Mirrors Mirrors are smooth reflecting surfaces There are 3 basic types of mirrors by shape; Flat: Used to change the direction of a ray or to create a virtual image of equal size Convex: (Curves out) Has a virtual focus always creates a smaller virtual image it is rarely used in telescopes

Concave: (Curves in) Used to gather light & focus it into a real focus, Creates an erect virtual and larger image of an object placed closer than its focus Create inverted real image Of an object placed farther away than the focus These images get smaller the farther away the object is Concave mirrors are often used in telescopes

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.