RP01: Stationary waves on a string Flashcards
What is a stationary wave?
A wave that stores, but does not transfer energy
How do stationary waves from on a piece of string?
Two waves with same wavelength, travelling in opposite directions, interfere with each other. When this occurs, they undergo superposition and a stationary wave is formed.
What is a node?
A node is a point of zero displacement in a standing wave.
They occur when two waves in antiphase and destructively interfere such that they completely cancel.
What is an antinode?
A point of max displacement in a standing wave.
Occur when two waves that are in phase constructively interfere.
Describe the arrangement of nodes and antinodes when the string is at fundamental frequency
One central antinode and a single node at each end.
What apparatus is used to generate a wave in a piece of string?
A vibration generator, driven by a signal generator
What apparatus used to alter length of string that is oscillating?
A bridge can be moved along to alter the length of the oscillating region
Why should the signal generator be operated for several minutes before use?
Signal generator needs time for the frequency to stabilise
What safety measures must you take?
A counterweight or g clamp should be used to produce counteracting moment that prevents stand from toppling over.
Never stand directly under a mass hanger, good practice to put padded bucket below hanger.
How does the length of the string affect the frequency of the first harmonic?
Inverse relationship between string length and frequency of first harmonic. As string length increases, frequency decreases.
How does the string’s mass per unit length affect the frequency of the first harmonic?
As mass per unit length increases the frequency of the first harmonic decreases
How does the tension in the string affect the frequency of the first harmonic?
As the tension in the string increases the frequency of the first harmonic increases
What equation is used to calculate the frequency of a string’s first harmonic?
f= (1/2l) sqrt(T/μ)
How can the tension in a string be varied?
Attaching a mass hanger at the end of the string. As masses added, tension will increase.
How can you measure the mass per unit length of a piece of string?
Measure the mass of a piece of string using a mass balance and then divide this by the length of the string.
What is the advantage of using a long piece of string when measuring the mass per unit length?
The longer the piece of the string, the power the percentage uncertainty in the measurement
Assuming all other factors remain constant, what is the effect of changing the frequency to double that of the first harmonic?
Result in the string resonating in its second harmonic
What equation is used to determine speed of wave?
v=fλ
When vibrating at fundamental frequency, what is the wavelength relative to the length of the oscillating string?
λ=2L
How can wave speed be calculated from the string’s tension and mass per unit length?
v= sqrt(T/μ)
When plotting a graph of T against L for a fundamental frequency, how can wave speed be determined?
Gradient will be L/T
Wave speed given by 2L/T so is 2 x gradient
