# physics midterm

## 59 terms

### simple harmonic (oscillatory) motion

back-and-forth vibratory motion

### sine curve

pictorial representation of a wave

### amplitude

distance from midpoint to the crest or trough of a wave

### frequency

number of vibrations an object makes in a unit of time (usually seconds) measured in Hz

### frequency formula

frequency = 1/period
period = 1/frequency

### transverse wave

wave in which motion of the wave is at right angles to the medium (i.e. electromagnetic radio waves)

### longitudinal wave

wave in which motion of the wave goes along the medium (i.e. sound waves)

### interference

can amplify or neutralize a wave
in phase = constructive
out of phase = destructive

### standing wave

a wave which has stationary parts; forms only if a multiple of half a wavelength fits exactly into the length of the vibrating medium

### node

stationary part of a standing wave

### antinode

position with the largest amplitude on a standing wave

### Doppler effect

apparent change in frequency due to the motion of the source
blue shift = increase in frequency
red shift = decrease in frequency

### infrasonic

sound waves below 20 Hz

### ultrasonic

sound waves above 20,000 Hz

### compression

an area of a longitudinal wave where the particles of the medium move close together, colliding to make a pulse of air

### rarefaction

a part in a longitudinal wave where the particles are spread apart, creating a gust of rarefied air in the opposite direction as compression

### sound transmission

solid, liquid, gas transmit sound
gas = higher temperature, lighter mass of particles, higher speed
solid, liquid = greater elasticity, higher speed (steel very elastic, putty inelastic)

### oscilloscope

measures sound waves in decibels

### decibel

dB; hearing damage begins at 85

### forced vibration

when an object is made to vibrate by a vibrating object nearby

### natural frequency

frequency at which an object vibrates when disturbed

### resonance

when a vibration forced on an object matches its natural frequency, increases amplitude

### beat

periodic variation in loudness of a sound

### photon

massless bundle of concentrated electromagnetic energy

distance/time

### electromagnetic wave

part-electric, part-magnetic wave

### infrared

electromagnetic rays with frequencies lower than visible light

### ultraviolet

electromagnetic rays with frequencies higher than visible light

### transparent

material whose atoms absorb and reemit light

### opaque

materials which turn light into random kinetic energy

where light rays cannot reach

### scattering

when light is absorbed and reemitted in all directions

### water

greenish-blue because it resonates with infrared and gradually filters out

### excited state

state with greater energy than the atom's lowest energy state

### spectroscope

analyzes light from glowing elements

### frequency/energy relations

frequency of photon or its color directly proportional to energy transmission of electron

### line spectrum

pattern of distinct lines of color, each line responding to a frequency of light

### reflection

return of a wave into its original medium

### law of reflection

angle of incidence = angle of reflection

### virtual image

image appearing in a location it cannot reach

### diffuse reflection

rough surface (greater than 1/8) scatters rays

### reverberations

multiple reflections of sound waves

### refraction

bending of a a wave crossing between two media
speed increase = away from normal
speed decrease = towards normal

### wave front

line representing positions of different crests in a diagram

### air

sound waves refract toward cool air

### mirage

image caused by refraction of light in Earth's atmosphere

### speed of light in air

speed of light in air .03% less than in a vacuum

### dispersion

separation of light into colors in a prism

### critical angle

angle of incidence that results in light being refracted at 90 degrees with respect to normal; emerging beam reduces to 0

### total internal reflection

complete reflection of light back into its original medium (critical angle)

### lens

piece of transparent material that refracts light

converging lens

diverging lens

### astigmatism

eye more curved in one direction than other; cylindrical corrective lenses curved more in different parts

### aberration

distortion in an image

### yellow-green

brightest color of sunlight

### complementary colors

two colors that combine to form white light

### subtractive primary colors

magenta, yellow, and cyan

### paints

when paints are mixed, the mixture absorbs all frequencies of each component