ipc ch17-18 vocab

mechanical wave

a disturbance in matter that carries energy from one place to another

medium

the material through which a wave travels

crest

the highest point of a wave above the rest position

trough

the lowest point below the rest position

transverse wave

a wave that causes the medium to vibrate at right angles to the direction in which the wave travels

compression

an area where the particles in a medium are pressed close together

rarefraction

an area where the particles in a medium are spread out

longitudinal wave

a wave in which the vibration of the medium is parallel to the direction the wave travels

surface wave

a wave that travels along a surface separating two media

periodic motion

any motion that repeats at regular time intervals

period

the time required for one cycle, a complete motion that returns to its starting point

frequency

the number of complete cycles in a given time

hertz

the unit of measure that frequency is measured in it is cycles per second

wavelength

the distance between a point on one wave and the same point on the next cycle of the wave

amplitude

the maximum displacement of the medium from its rest position

reflection

happens when a wave bounces off a surface that it cannot pass through

refraction

the bending of a wave as it enters a new medium at an angle

diffraction

the bending of a wave as it moves around an obstacle or passes through a narrow opening

interference

occurs when two or more waves overlap and combine together

constructive interference

occurs when two or more waves combine to produce a wave with a larger displacement

destructive interference

occurs when two or more waves combine to produce a wave with a smaller displacement

standing wave

a wave that appears to stay in one place- it does not seem to move through the medium

node

a point on a standing wave that has no displacement from the rest position

antinode

a point where a crest or trough occurs midway between two nodes

sound waves

longitudinal waves- compressions and rarefractions that travel through a medium

intensity

the rate at which a wave’s energy flows through a given area

decibel

a unit that compares the intensity of different sounds

loudness

a physical response to the intensity of sound, modified by physical factors

pitch

the frequency of a sound as you perceive it

sonar

a technique for determining the distance to an object under water

Doppler effect

a change in sound frequency caused by motion of the sound source, motion of the listener, or both

resonance

the response of a standing wave to another wave of the same frequency

electromagnetic waves

transverse waves consisiting of changing electric fields and changing magnetic fields

electric field

this field exerts electric forces on charged particles in a region of space

magnetic field

this field produces magnetic forces in a region of space

electromagnetic radiation

the transfer of energy by electromagnetic waves traveling through matter or across space

photoelectric effect

the emission of electrons from a metal caused by light striking the metal

photons

packets of electromagnetic energy

intensity

the rate at which a wave’s energy flows through a given unit of area

electromagnetic spectrum

the full range of frequencies of electromagnetic radiation

amplitude modulation

means the amplitude of the wave is varied

frequency modulation

means the frequency of the wave is varied

thermograms

are color-coded pictures that show variations in tempurature

transparent

means that the material transmits light

translucent

this means the material scatters light

opaque

means the material either absorbs or reflects all of the light that strikes it

image

a copy of an object formed by reflected waves of light

regular reflection

this occurs when parallel light waves strike a surface and reflect all in the same direction

diffuse reflection

occurs when parallel light waves strike a rough, uneven surface, and reflect in many different directions

mirage

a false of distorted image.

polarized light

light with waves that vibrate in only one plane

scattering

this means that light is redirected as it passes through a medium

dispersion

the process in which white light separates into colors

primary colors

three specific colors that can be combined in varying amounts to create all possible colors. These colors are red, green, and blue

secondary color

a combination of two primary colors

complementary colors of light

any two colors of light that combine to form whit light

pigment

a material that absorbs some colors of light and reflects other colors

complementary colors of pigments

any two colors that combine to make black pigment

luminous

objects that give off there own light