Physics Test 4: Waves, Sound and Light Flashcards
What is a wave?
A disturbance or variation that travels through a medium
What’s a longitudinal wave?
Particles move in the same direction as the energy. Think a slinky
What is a transversal wave?
Particle is displaced perpendicular to the direction of energy. Think crests and troughs
What’s the equation for the speed of sound?
V = 331.29 + 0.59t
t = temperature
Frequency of a wave is determined by…
Frequency of the vibrating source.
What is a mechanical wave?
Mechanical waves are waves which propagate through a material medium (solid, liquid, gas)
What does wave speed depend on?
Elastic and inertial properties of the matter
What happens during reflection?
The wave reflects at the angle it hits at. If it hit at a crest, it becomes a trough and vice versa
What are real world examples of transverse and longitudinal waves?
Transverse: Water, light, radio
Longitudinal: Sound, earthquakes
What does the size of a water wave depend on?
Amplitude
What are the 3 types of waves?
Mechanical (longitudinal and transversal)
Electromagnetic ( x rays)
Matter waves (quantum)
What is lamda?
Wavelength (from crest to crest or trough to trough)
What is frequency?
of cycles / second
What is velocity in respect to waves?
Speed each crest moves
What is the period of a wave?
Time for one complete cycle (T = 1/F and F = 1/T)
What is constructive interference?
When two waves overlap and their displacements are in the same direction (crest on crest, trough on trough)
What is destructive interference?
When two waves overlap and their displacements are in opposite directions (crest on trough). They cancel each other out
What is amplitude?
Distance between equilibrium and crest
What determines amplitude?
Energy
What is the wavelength for the first harmonic (the fundamental frequency) in an open tube?
L = 1/2 lamda
What is the wavelength for the first harmonic in a closed tube?
L = 1/4 lamda
What are nodes?
The point of max destructive interference is
What is resonance
When two things vibrate that their frequencies are in phase
What are beats?
Changes in amplitude when you have two waves of close frequency
What is beat frequency?
The difference between the frequencies of two waves. Frequency of the beat = | F2 - F1|
What does the spacing equal?
1/2 lamda in open tube
1/4 lamda in closed tube
What is pitch?
The brain’s interpretation of frequency?
What is the Doppler Affect
Apparent changes in frequency of a wave caused by relative motion between the source of the wave and an observer
When frequency is larger there is a…
Higher pitch
What is the formula for calculating the Doppler Affect?
F2 = f1 ( V + (vd) / V - (vs) )
V = Speed of sound
F2 = Shifted frequency
F1 = Original frequency
VD = Speed of detector
VS = Speed of source
If the sound is coming towards you, VS and VD are positive
If the sound is going away from you, VS and VD are negative
