Physics Unit 5 - Waves

Waves vocabulary

Cycle

distance between two consecutive points on a wave that (from crest to crest or trough to trough)

Oscillation

the displacement/vibration of a wave

Amplitude

distance from midline to crest

Period

one wavelength in a displacement/time graph

Wavelength

distance between two consecutive points on a wave that are in phase, such as the distance between two adjacent peaks (lambda λ) in meters (m)

Frequency

the number of complete wavelengths that pass a point in a given time

Crest

maximum point in a transverse wave

Trough

minimum point in a transverse wave

Velocity Formula for a wave

v = fλ

Transverse Wave

wave energy runs perpendicular to wave distance

Longitudinal Wave

displacement parallel to distance

Electromagnetic Spectrum

transverse waves (radio, visible, and gamma) where energy can be transmitted though empty space (vacuum)

Reflection

waves bounce from smooth, flat surfaces to reflect an image (when light rays bounce back) or produce an echo (sound waves bounce back)

Refraction

needs 2 mediums where a ray will go through the different mediums and change speed and direction because of the different densities

Diffraction

waves going through a barrier with a gap (big or small) and change direction

Intensity

amount of energy in a wave (decibels)

Timbre

how well music/sound comes across in harmony (sound quality)

Pitch

how high or low a sound is (depends on frequency + is how fast molecules vibrate)

over 20,000 Hz = ultrasonic sound

Longitudinal vs. transverse waves

**Longitudinal**: displacement/direction

**Transverse**: displacement/time

Mechanical vs. EM Waves

**mechanical**: *not capable* of transmitting energy through empty space

**EM**: *can* transmit energy through empty space

Sound vs. light

Sound:

• mechanical waves

• require a medium to travel through (air or water)

• longitudinal waves = particles in the medium vibrate parallel to the direction of wave propagation

• lower frequencies and bigger wavelengths

Light:

• electromagnetic waves

• can travel through a vacuum (empty space)

• transverse waves = particles in the medium vibrate perpendicular to the direction of wave propagation

• higher frequencies and smaller wavelengths

Colors of light

ROYGBIV

red

orange

yellow

green

blue

indigo

violet

Usage of the different wavebands of EM Spectrum

**radio waves**: radios and TVs (longest wavelength)

**microwaves**: used for heating

**infrared radiation**: used for heating

**visible light**: narrowband of wavelengths that humans can see (ROYGBIV)

**ultraviolet radiation**: absorbed by/harmful for skin

**X-rays**: used to see through objects/bodies

**gamma rays**: harmful + used to treat cancer (smallest wavelength)

Doppler Effect, when is the frequency higher? Lower? Why?

Change in frequency & pitch of a sound due to observer/sound source’s motion

frequency = higher when sound source moving towards receptor ***vs.*** lower when sound source moving away from receptor

3 properties of sound

Intensity, Pitch, Timbre