Light and Optics Topic 3

Lasers

used to make incisions in surgery

X-rays

used to view dense structures in the body

gamma rays

used to treat cancer

Amplitude

Height of a wave

Wavelength

the distance from one crest of a wave to the next

Frequency

the number of times the medium vibrates in a given unit of time

electromagnetic radiation

all forms of radiant energy: visible light, infrared radiation, ultraviolet radiation, radio waves, x-rays etc.

electromagnetic spectrum

refers to the whole range of wavelengths of visible and invisible electromagnetic radiation.

radio waves

vital for communication. The longest radio wave has a wave length of 100 km. FM waves are longer than AM waves. can also be used to produce medical image of inner tissues.

microwaves

shorter than radio waves, but carry more energy. microwaves make water particles vibrate in food causing the food to heat up.

infrared waves

unseen but felt as heat. Special equipment can sense infrared radiation- these images are called thermograms.

Ultraviolet Light (UV)

can burn skin. Most of the sun's UV rays are absorbed by the O zone layer. Sunblock can be uses to prevent UV rays from getting to your skin.

X-rays and gamma rays

extremely high energy. X-rays don't penetrate bone, while gamma rays are used to kill cancer cells.

Thomas Edison

Invented the light bulb

Incandescent light

form of artificial light; uses electrical energy to heat a thin wire thread (filament) that glows white hot.

fluorescent light

form of an artificial light; uses ultraviolet light waves to make the coating (phosphor) inside an opaque tube glow white.

phosphor

substance that emits light when exposed to ultraviolet radiation

Phosphorescent light

slightly different form than fluorescent light, in that it stores radiant energy even after the source of radiation is gone. this form of light is often found in glow in the dark items.

Bioluminescence

the ability of certain organisms to produce light by chemical reaction.

primary colours

re, green and blue light; adding these three colours of light produces white light.

secondary colors

yellow, cyan, and magenta; colours made from adding any two primary colours of light.

Theory of Colour Addition

theory that explains what happens when coloured lights are mixed together

theory of colour subtraction

theory that explains what happens when white light is passed through or reflected off a dyed surface.