Light key terms

Electromagnetic wave

Vibrating electric charge that produces a wave that is partially electric and partially magnetic and carries energy

Visible spectrum

Visible light; range on electromagnetic spectrum between infrared and ultraviolet

Light

Electromagnetic wave that travels at a constant speed; form of energy that travels through space in a straight line

Ray

Used to represent light waves since light only travels in a straight line

Galileo Galilee

Began his study of physics late in life; one of the first great scientists of physics

Ole Romer

Astronomer; accidentally measured the speed of light while studying the moons of Jupiter

Albert Michelson

First American to revive the Nobel prize in physics; most famous experiment to determine the speed of light; easy to repeat except for distances used

Speed of light

3×10^8; constant throughout the universe

Light year

Distance light travels in one year; 9.5×10^15 meters

Luminous

Emits light

Incandescent

Emits light due to heating

Vapor

Emits light due to exciting vapor or gas electrically

Fluorescent

Emits light due to exciting mercury and inert gas electrically

Illuminate

Reflection of light rays

Transparent

Light ray passes through with no distortion or 100% transmission

translucent

some light rays pass through with distortion

opaque

no light rays pass through

absorption

to take in light; causes objects to heat up

diffraction

the bending of a light ray due to a slit or obstruction

polarization

the aligning of vibration in a transverse wave

reflection

bouncing of a light ray

law of reflection

the angle in equals the angle out; angle of incidence equals the angle of reflections; angles are measure from the normal

normal

line drawn perpendicular to the change in medium

refraction

the bending of a light ray due to a change in medium

index of refraction (n)

ratio of speed of light in a vacuum to speed of light through a medium

snell’s law

determines the amount of refraction of light between two media where 1 is the incident ray and 2 is the refracted ray

critical angle

angle that causes refracted ray to lie along the boundary of different media

total internal reflection

100% reflection (no transmission) of light that strikes the boundary between two media at an angle greater than the critical angle

Socrates and Plato

400 bc

eyes shoot out streamers

particle

Empedocles

450 bc

asserted light to be a very high-speed wave

waves

Isaac Newton

mid 1600’s

color

wave

Christian Huygens

mid 1600’s

overlap of waves/ proposed wave theory

wave

Thomas Young

helped us understand how we see colors/light was emitted from a source in all directions as a series of waves.

wave

Albert Einstein

mid 1900’s

photo electric effect

photon

a packet of light energy

photoelectric effect

the liberation of an election; links photons to light emission

wave theory

theory that defines light as a wave

explains light in terms of straight line travel, reflection, refraction, diffraction, interference, polarization, and changing speeds through varying media

particle theory

theory that defines light as a particle

explains light in terms of straight line travel, the non-interaction of rays, reflection, light exerting pressure, light emissions, photons, and not requiring a medium

Max Planck

defined light as both a wave and a particle

quantum theory

energy is proportional to frequency; supports wave particle theory

wave-particle theory

duality theory; theory that defines light as a particle (photon) carried on a wave