Physics Lect 6
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Wave formulas relating frequency and wavelength
 v = f λ
 velocity = (frequency)(wavelength)
 use only to find frequency or wavelength, velocity is independent of these two

Frequency
the # of waves that pass a fixed point per second

Period
 the # of seconds it takes for a complete wavelength to pass a fixed point
 T = 1 / f

What factors affect the speed of a wave
 Only medium affects the velocity of a wave
 (1) its elasticity (resistance to change in shape)  stores U  greater eleasticity speeds waves up
 (2) its inertia (resistance to change in motion)  stores K.E.  greater inertia slows waves down

Generally, stiff mediums ___ ___ waves.
speed, up

Generally, heavy mediums ___ ___ waves.
slow, down

What effect does temperature have waves traveling through a gas?
It increases velocity as it increases (more K.E.)

Velocity relates to what for surface waves?
with surface waves, velocity increases with depth

What is the elastic component of surface waves?
gravity

How is power measured?
 Power is measured in terms of intensity (I)
 I is proportional to A^{2} and f^{2} for all waves
 It is related to itself  dB (decibles)
 ~ however many zeros you add to an intensity  take that integer and add a zero behind it, this will give you the decible jump

Beats
 occurs when two waves with slightly different frequencies interfere with eachother
 at some points there are "in phase" (constructive) and sometimes they are out of phase (destructive)
 f_{beat} =  f_{1}  f_{2} 

Pitch
 For sound waves, pitch correlates with frequency
 A high note will have a high pitch and a high frequency

What happens to waves at an interface of media?
 (1) some (or all) of the energy is REFLECTED
 if it is reflected off of a more dense medium than the medium it is coming from > the wave is inverted (180° phase shift)
 if it is reflected off a less dense medium > the wave reflects back upright (no phase shift)
 (2) the remaining energy is REFRACTED into the new medium
 these waves will have the SAME frequency, a DIFFERENT wavelength, and a SMALLER amplitude

Standing Waves
 waves that contain nodes and antinodes
 node is "still" when observed
 antinodes have the greatest displacement from zero

Harmonic series
 a list of wavelengths that create standing waves for a specific length of "string"
 listed from largest to smallest
 ∴ 1st has the longest λ and the fewest nodes (2)
 if both ends are secure:
 L = nλ_{n} / 2 (n = 1, 2, 3...)
 if one end is loose:
 L = nλ_{n} / 4 (n = 1, 3, 5...)

Simple Harmonic Motion
 motion that demonstrates a sine function of time
 objects in simple harmonic motion share certain properties: 1) acceleration is ∝ displacement but opposite in sign; 2) a & d are related by f^{2}; 3) oscillates between kinetic and potential E

The Doppler Effect
when a source moves relative to the observer it can change the frequency and the wavelength of the wave that reaches the observer

Doppler Effect Formulas
 Δf / f_{s} = v / c
 Δλ / λ_{s} = v / c
 f_{s}: frequency produced by the source
 λ_{s}: wavelength produced by the source
 v: the net speed of the source and the object (if they are moving in the same direction you subtract their velocities; if they are moving in opposite directions you add their velocities)

With the Doppler Effect, what happens as the source and the observer grow closer?
The frequency increases and the wavelength decreases

What experiences no Doppler Effect?
 Objects moving in the same direction at the same speed
 v = 0 (because if they are moving in the same direction we subtract their speeds)