Download UNIT 3 LIGHT AND OPTICAL SYSTEMS

UNIT 3 LIGHT AND OPTICAL SYSTEMS
TOPIC 1 WHAT IS LIGHT?
LIGHT- form of energy that you can see
NATURAL LIGHT SOURCE- light from the sun
RADIATES- spreads out energy called RADIATION
RADIANT ENERGY- energy such as light that travels by radiation
ARTIFICIAL LIGHT SOURCE- light from a bulb
INCANDESECT SOURCE- when an object can be heated to such a high temperature that it
emits visible light
INCANDESCENCE- the emission of visible light by a hot object
INCANDESCENCE ENERGY TRANSFORMATION:
ELECTRICAL ENERGY
ENERGY
THERMAL ENERGY
VISIBLE LIGHT
FLUORESCENCE- when high-energy, invisible ultraviolet light is absorbed
FLUORESCENCE ENERGY TRANSFORMATION:
ULTRAVIOLET LIGHT
LIGHT ENERGY
ENERGY ABSORBED
VISIBLE
BY PARTICLES
FLUORESCENT ENERGY TRANSFORMATION:
ELECTRICAL ENERGY
ENERGY ABSORBED BY MERCURY PARTICLES
ULTRAVIOLET LIGHT ENERGY
ENERGY ABSORBEDF BY PHOSPHOR PARTICLES
VISIBLE LIGHT ENERGY
PHOSPHORESCENCE- the persistent emission of light following exposure to and removal of a
source of radiation
CHEMILUMINESCENCE- when a chemical reaction produces energetic particles that give of
visible light energy
BIOLUMINESCENCE- when animals produce chemical reactions inside their bodies to provide
energy for light
LUMINOUS- EMITS LIGHT
NON-LUMINOUS- DOES NOT EMIT LIGHT
RAY- is a straight line that represents the path of a beam of light
RAY DIAGRAM PAGE 185 FIGURE 3.11
TRANSPARENT- light passes through ex. Glass
TRANSLUCENT- blocks some of the light ex. Wax paper
OPAQUE- blocks all light and prevents it from passing through ex. Wall
TOPIC 2 REFLECTION
REFLECTION- the process in which light strikes a surface and bounces back off that surface
INCIDENT RAY- the ray that comes from a light source and strikes the surface
REFLECTED RAY- ray that bounces off the surface
NORMAL LINE- a reference line drawn perpendicular to a reflecting surface at the point where
an incident ray strikes the surface
ANGLE OF INCIDENCDE- the angle between the incident ray and the normal line
ANGLE OF REFLECTION- the angle between the normal line and the reflected ray
PLANE MIRROR- flat surface
LAW OF REFLECTION- the two main predictable behaviours of reflected light: 1. The angle of
reflection (r) is equal to the angle of incidence (i) 2. The incident ray, the normal, and the
reflected ray are always in the same plane.
CONVEX- mirrors that bulge out
CONCAVE- mirrors that cave in
VIRTUAL IMAGE- an image located where reflected rays only seem to originate
TOPIC 3 REFRACTION
REFRACTION- bending of light when it travels from one medium to another
ANGLE OF REFRACTION- in optics, the angle between the normal and the refracted ray
TOPIC 4 LENSES AND VISION
CONCAVE LENS- thinner and flatter in the middle than around the edges
CONVEX LENS- thicker in the middle that around the edges
FOCUSSES- brings them back to a point
RETINA- area at the back of the eye
NEAR-SIGHTED- have trouble seeing distant objects
FAR-SIGHTED- have trouble seeing objects close to them
ACCOMODATIONS- they process of changing the shape of the lens to adjust for different object
distances
NEAR POINT- the shortest distance at which an object is in focus
FAR POINT- the longest distance at which an object is in focus
The DIAPHRAGM is the device that controls the APERTURE (opening) of a lens or optical
system. The SHUTTER is a device that limits the passage of light
IRIS- in the eye, the coloured ring; works like the diaphragm of a camera
PUPIL- the opening in the eye; appears as the dark centre of the eye
IRIS REFLEX- the natural adjustment in the size of the pupil
OPTIC NERVE- the nerve that connects the eye to the brain
BLIND SPOT- the point where the optic nerve enters the retina; has no light-sensing cells
TOPIC 5 EXTENDING HUMAN VISION
REFRACTING TELESCOPE- a telescope having a convex lens to collect and focus light from a
distant object, and a eyepiece lens to magnify the image
OBJECTIVE LENS- the convex lens in a refracting telescope or microscope
EYEPIECE LENS- in a telescope or microscope, the lens that works as a magnifying glass to
enlarge the image
REFLECTING TELESCOPE- a telescope having a concave mirror to collect rays of light from a
distant object
OBJECTIVE MIRROR- the mirror in a reflecting telescope; also called the primary mirror
PRISMS- in binoculars, glass blocks serving as plane mirrors; allow binoculars to be made
shorter than telescopes
TOPIC 6 THE SOURCE OF COLOURS
SPECTRUM- when white light is refracted into different colours, the resulting pattern is a
spectrum
SOLAR SPECTRUM- the pattern of colours in sunlight: red, orange, yellow, green, blue, indigo
and violet
ADDITIVE PRIMARY COLOURS- the three colours red, green, and blue
SECONDARY COLOURS- yellow, cyan and magenta
RODS- in the retina of the eye, a cylinder-like cell that detects the presence of light
CONES- in the retina of the eye, a cone-shaped cell that detects colour
COLOUR BLINDNESS- unable to detect colour
TOPIC 7 THE WAVE MODEL OF LIGHT
CRESTS- high part of water wave
TROUGHS- low part of water wave
WAVELENGTH- the distance from crest to crest or from trough to trough
AMPLITUDE- the height of the crest or the depth of the trough from the rest position
FREQUENCY- the rate at which the duck and the water move up and down (see figure 3.57 page
239) the frequency is the number of cycles completed by a vibrating object in a unit of time
WAVE MODEL OF LIGHT- a way of explaining the behaviour of light; involves picturing it
travelling as a wave
LASER- light amplification by the stimulated emission of radiation
INCOHERENT- referring to light, having many different wavelengths or one wavelength but the
waves are not lined up eg incandescent light
COHERENT- referring to light, having only one wavelength, with all waves lined up in a similar
patter eg laser light
TOPIC 8 BEYOND LIGHT
ELECTROMAGNETIC SPECTRUM- the arrangement by wavelength of the different forms of
electromagnetic radiation, including visible light energy
INFRARED RADIATION- heat radiation, anything that is warmer than its surroundings emits
infrared rays
RADIO WAVES- any electromagnetic wave that is useful for carrying sounds or pictures through
the air from a transmitter to a receiver
MICROWAVE- have the shortest wavelength and the highest frequency of all radio waves
ULTRAVIOLET (UV) RADIATION- wavelengths of 200nm beyond violet light in the
electromagnetic spectrum (nm=nanometer); cases tanning
OZONE LAYER- a “blanket” of ozone (a form of oxygen) surrounding Earth about 20-25 km
above the ground acts like a filter, absorbing much of the Sun’s ultraviolet light
X-RAY- electromagnetic radiation having a very short wavelength; can penetrated substances
such as skin and muscle
RADIATION THERAPY- the use of gamma rays to destroy cancer cells