Flashcards in Statioanary Waves Deck (25):
How are they formed ?
They are formed when the reflected wave reinforces the initial wave at the resonant frequency.
Progressive waves is reflected at the boundary .
Stationary waves .
Store energy in resonator
Fixed patterns of nodes and antinodes
Oscillations of different amplitudes occur along the length of wave in a pattern that does not change .
What happens when Frequency is high ?
The wavelength gets smaller.
What is the distance between the node and the adjacent antinode ?
Two waves sources which have constant phase difference and same frequency and same waveform .
What is resonance and what do they do ?
Store wave energy by reflecting the wave back on itself to form a stationary wave pattern.
How can a resonator be set in Stationary waves ?
Stationary waves motion by sudden impact that transfers large amounts of energy in instant which is stored in waves
Effect of the resonance
Small amount of energy is collected over a period of time can be stored up in the stationary waves building larger amplitude .
How does resonance occur ?
Occur when wave energy coming in from outside has a forcing frequency equal or close to natural frequency .
Has a number of frequency naturally vibrate .
Natural frequencies which are known as harmonics of the guitar string .
Fundamental frequency is lowest possible frequency .
Use transverse waves in stretched strings to make
What di pipe organs, woodwind and brass use and why ?
They all use longitudinal waves because the sound waves travel in the tube or pipe to make resonators in the form of compression or rarefaction .
Open end in both end
λ=L/2n -Complete set
You cannot control the speed of wave ,fixed speed of the sound in air you can alter the length tho.
Closed one end of pipe
Nodes and antinodes both present.
Has one end open and the other end to sound out .
This gives a lower musical note .
Fundamental harmonic will have just quarter wavelength fitting as well as only odd numbers harmonics will fit in the pipe .
Such as λ/4
L=3λ/4, 5λ/4 ,7λ/4,
Instrument of string use transverse waves in stretched strings to make resonators .
The fixed end of the string are always nodes
The fundamental mode has one antinode so L=λ /2
Thicker strings with more mass per unit length gives a slower speed and hence a lower note
Tighter strings with more tension , gives a faster speed and hence a higher note
Uses of Resonators
Reflections of the TV signals create a node at the reflector Dipole detector placed at the an antinode.
Microwave : a resonator cavity is used to build microwave power reflections inside oven cooking causing hot spots antinodes /cold spots nodes food is usually rounded a turnover .
What is the difference between a progressive wave and a stationary wave ?
Stationary waves stores energy and has a fixed pattern of nodes and antinodes
Stationary waves all particles except node vibrate at the same frequency .
Amplitude varies from node to antinode.
Progressive waves transmits energy has a moving pattern of displacements .
Amplitude same for all particles
All particles vibrate at the same frequency.
Explain how and why TV antennas make use of stationary waves ?
Reflecting the wave back on itself creates a stationary wave the position of the first antinode gives a large amplitude signal
Resonance in Musical instruments
Brass instruments involve the blowing of air into the mouthpiece .They vibrate of the lips against the mouthpiece produces a range of frequencies
One of the frequencies in the range of frequencies matches one of the natural frequency of the air column inside of the brass instruments .
It forces the air inside of the column into resonance vibrations .Resonance vibrations .Leading to a bigger vibration and loud sound.
Tube is curled to reduce the size of the instrument .
Length can be adjusted by sliding the tube to increase and decrease its length or by opening and closing holes locate along the tube in order to take control where the air enters and exists the tube .
When air is blown through a woodwind instruments the reed vibrates producing turbulences range of vibrational frequencies .
The result of resonance is a big vibration when the frequency of the vibration of the reed matches the frequency vibration of the air column in straw resonance occur .
The length of the air column is controlled by opening and closing holes within metal tubes .
Higher pitch is caused when the straw is shortened
Harmonics 1-Fundamental Frequency
Has 2 nodes and 1 antinode
It can be seen as 2 over 1 as the wavelength λ
3 nodes and 2antinodes
λ = 2/2
4 Anti nodes
2 /4 λ
λ = 2/5
Explain why the wave speed Is unaltered ?
tension and mass per unit length of the string are still the same .