Physics 11 - Waves

Type A/B: First Harmonic

λ = 2L and f = v/2L

Type A/B: Second Harmonic

λ = L and f = v/L

Type A/B: Third Harmonic

λ = (2/3)L and f = 3v/2L

Type A/B: Nth Harmonic

λ = 2L/N and f = N (v/2L)

Type C: First Harmonic

λ = 4L and f = v/4L

Type C: Second Harmonic

λ = (4/3)L and f = 3v/4L

Type C: Third Harmonic

λ = (4/5)L and f = 5v/4L

Type C: Nth Harmonic

λ = 4L/(2N-1) and f = (2N-1) x (v/4L)

Transverse Waves

Move up and down perpendicular to the direction of propagation (ex. shaking a rope)

Longitudinal Waves

Move back and forth in the same direction of propagation (ex. spring, sound; acts like ripples)

Mechanical Waves

Require a medium in order to transport their energy

Electromagnetic Waves

Do not require a medium, can travel through a vacuum (ex. radio, micro, infared, ultraviolet, x-ray, gamma, visible light)

The greater the amplitude of a wave…

…the greater the energy transported by the wave

Wave speed vs. Particle speed

Wave speed is how quickly the disturbance travels through a medium, particle speed is how quickly a particle moves about it's equilibrium position

What does wave speed depend on?

the medium

What does frequency depend on?

the source of the wave

The amplitude of the incident wave is than the amplitude of the reflected/transmitted waves, and _ to the amplitude of the reflected + transmitted

greater, equal

When a wave changes medium…

… the speed changes but the frequency does not

Transmission from less to more dense

The reflected wave is inverted upside down

Transmission from more to less dense

The reflected wave is not inverted

Fixed end reflection

The reflected wave is inverted, almost all the energy is reflected and amplitude is nearly identical

Free end reflection

The reflected wave is not inverted, almost all the energy is reflected and amplitude is nearly identical

Node

positions where the wave does not vibrate

Antinode

positions where the wave vibrates with maximum amplitude

natural frequency

a.k.a. harmonics, the specific standing waves that can occur in a region

Resonance

A phenomenon that occurs when two objects naturally vibrate at the same frequency. Resonance causes the system to oscillate with increased amplitude

Beats

when two sound waves of unequal but close frequencies are played, there will be an alternating constructive and destructive interference

Constructive interference

when waves add up to make a larger amplitude

Destructive interference

when waves don't match up and cancel each other out to make a smaller amplitude

Beat equation

fbeat = |f1 - f2|

Doppler effect

An observed change in the frequency of a wave when the source or observer is moving

Object is coming towards you

Higher pitch - shorter wavelength, higher frequency

Object is moving away from you

Lower pitch - longer wavelength, lower frequency

Ray

A ray is a straight line with an arrow pointing in the direction the wave is travelling

Wavefronts

Lines/curves representing corresponding points on a wave that vibrate in unison

Law of reflection

angle of incidence = angle of reflection for waves reflected by a barrier

Refraction

the change in direction of a wave at the boundary between two different media (ex. air to water)

Diffraction

the spreading of waves around the edge of a barrier (ex. sound waves bending around a corner)