Spectrum Terms

Electromagnetic waves: Waves that do not require a medium.

Law of reflection: The angle of incidence is equal to the angle of reflection. Both are measured from a line perpendicular to the surface called the normal.

Light

Photons: Particles of light.

Speed of light: Generally decreases as medium increases in density. Examples include the following:

Vacuum — 3.00 x 10⁸ m/s

Water — 2.25 x 10⁸ m/s

Glass — 1.97 x 10⁸ m/s

Intensity: Brightness that decreases as distance from the origin increases because photons are spreading over a wider area.

Lasers: A divide that controls the way energized atoms release photons.
The word laser comes from the phrase light amplification by stimulated emission of radiation.

Monochromatic lasers: One specific color.

Coherent lasers: Organized. Colors move in step with each other.

Directional lasers: Tight beam, strong and concentrated.

Longitudinal waves: Particles in a medium move parallel.

Compression: When particles are closest together.

Rarefraction: When particles are spread farthest apart.

Mechanical waves: Waves that require a medium.

Medium: The matter through which a wave travels. The actual medium is not moving; it just has energy moving through it.

Parts of a wave:

Amplitude: Greatest distance from the natural resting position.

Crest: Point of maximum displacement.

Frequency: Number of hertz that pass a certain point in one second.

Hertz (HZ): Unit that measures speed of wave (cycles per second).

Period: Time required for one full wavelength to pass a given point. Symbol is T. Unit is in seconds.

Trough: Point of minimum displacement

Wavelength: Distance between two equivalent parts of the wave. Unit is meter and symbol is lambda .

Simple harmonic motion (SHM): The repeating cycle that allows a mass on a spring to bounce forever (neglecting friction).

Surface waves: Particles move in circles. They move differently because they occur at the boundary between two media.

Transverse wave: Particles in medium move perpendicular to the movement of energy.

Wave: A disturbance that carries energy through matter or space.

Wave interactions:

Interference: Waves that exist in the same place at the same time.

Constructive Interference: Two crests or two troughs will add together to make a larger crest, not average out.

Destructive interference: Crest meets trough and causes the amplitude to be smaller or completely cancel it out.

Diffraction: The bending of a wave as if passes an edge or an opening. This is why you can hear sound around a corner.

Doppler Effect: The apparent change in frequency of a moving object to the observer.

Reflection: The bouncing back of a wave when it meets the surface of boundary.

Refraction: The bending of waves as they pass from one medium to another.

Wave movement: Waves travel from their point of origin equally in all directions. Energy spreads out as it moves away from the origin, decreasing in intensity as it spreads.