level 3 waves Flashcards
Types of waves
transverse (light) and longitudinal (sound)
Longitudinal waves
particles oscillate in the same direction as the wave move.
V term in the wave equation
Wave speed (ms-1)
either light or sound
f term in the wave equation
equation
Frequency (Hz)
λ term in the wave equation
Wavelength (m)
Diffraction
The bending of waves as they pass through a gap or slit
Amplitude
The energy carried in a wave
Interference
When 2 or more waves meet in some medium. Interference occurs and a resultant wave form is created
Transverse waves
particles are moving at 90 to the direction of wave movement
The wave equation
v=fλ
Constructive Interference
Constructive Interference occurs when 2 waves meet in phase (crest meets crest or through meets through) resulting in a greater amplitude.
Destructive interference
Destructive interference occurs when 2 waves meet out of phase (crest meets through) resulting in reduced amplitude.
The double slit equation when θ is less than 10
nλ=dx/L
d in the double slit equation when θ is less than 10
Slit separation (m)
x in the double slit equation when θ is less than 10
Fringe separation (m)
L in the double slit equation when θ is less than 10
Length from slit to screen (m)
The double slit equation when θ is greater than 10
nλ=dsinθ
What would happen if slit separation increased?
If wavelength and screen distance (L) stay constant, but slit separation (d) increases the distance between the adjacent bright spots reduces and the bright fringes get closer together.
What would happen if the screen is moved further away?
If wavelength and slit separation (d) stay constant and screen (L) moves further away then the distance between bright will decrease Fringes get closer together.
What would happen if Lazar changes from red to violet light?
Red diffracts more than violet. When d and L stay constant a change to violet means the wavelength has decreased. This means theta decreases so the pattern becomes closer together.
What would happen more slits are added?
More slits means antinodes are brighter. Because there are more sources of light the antinodes are brighter. More waves means more chance of destructive interference. Brighter antinodes mean nodes are clearer and more defined.
What happens when white light is shone through slits?
White light is made of ROYGBIV, all these have a different wave length. Wavelength then diffracts at different angles. Each wavelength interacts differently with the slit. This results in the separation of white light into its constituent colours, a phenomenon known as dispersion.
What happens when the central bright spot is n=0?
This is where all waves meet in phase, constructive interference occurs and a antinode forms. This is the brightest antinode in the pattern.
What must nmax always be?
Nmax must always be a whole number so you must round DOWN.
How do you calculate the maximum number of fringes that can be used?
nmax = d/wavelength
How are standing waves formed?
Standing waves are formed when a travelling wave encounters a boundary and is reflected back. Causes interference with the incoming reflected wave, which sets up the standing wave (appears stationary)
What are the rules for standing waves?
Waves must have the same wavelength and frequency.
Waves must be the same amplitude.
Waves must be travelling in opposite directions.
Standing wave boundaries: Fixed
Wave is reflected 180 out of phase.
Causes destructive interference.
Node is formed.
Standing wave boundaries: Open
Wave is reflected back in phase.
Causes constructive interference.
Antinode is formed.
Types of ‘instruments’ that form standing waves.
Fixed end.
Open/Open end.
Open closed end.
What do fixed end standing waves look like?
Both ends are fixed causing Nodes to form and both ends.
What is the fundamental wavelength equation?
wavelengthxfrequncy = 2xL
What is the frequencies on harmonics equation?
fn = nFf
What is fn in frequencies on harmonics equation?
Frequency of harmonic (Hz)
What is different about the speed of sound on a string?
The speed of sound is not constant on a string. It can change due to; tension of the string, thickness of string (mass per metre).
What is the equations for speed of sound on a string?
v= square root of T/m
What is the unit for m in the equation for speed of sound on a string?
kgm-1
What do open/Closed standing waves look like?
They have one closed/fixed end and one open end.
What is the only harmonics that open/closed waves can form?
open/closed pipes can only form odd harmonics as they must end in a node and antinode.
How do open/closed harmonics sound compared to fixed string or open/open pipes?
The sounds produced is less rich than fixed string or open/open pipes as less harmonics are able to form.
What are two reasons wave speed can change in pipes?
Medium (eg water making sound travel faster)) and temperature (warmer air making sound travel faster)
What is timbre affected by?
Shape of the instrument and material used to make instrument.
