wave behaviour - standing waves Flashcards
When do standing waves occur?
superposition of two identical waves travelling in opposite directions
When are stable interference patterns seen?
When waves are coherent
What is an antinode?
Where waves combine to make a larger oscillation
open points on diagram
What is a node?
Where waves add to zero
crossing points on diagram
What is the spacing of nodes and antinodes?
half a wavelength
What is the fundamental?
The lowest frequency which can form a standing wave
What sounds can be heard other than the fundamental?
Harmonics - higher frequencies which from shorter wavelength standing waves in the same space
What happens at the ends of a space with two fixed ends?
A node at either end
What is the formula for frequencies with two fixed ends?
fn = nf1
What can the fundamental be represented by?
f1
What is the formula for length of space with two fixed ends?
L = 1/2 n wavelengths
Give a musical example of a space with two fixed ends
guitar string
What happens at the ends of a space with two open ends?
An antinode at either end
What is the formula for frequencies with two fixed ends?
fn = nf1
What is the formula for length of space with two fixed ends?
L = 1/2 n wavelengths
Give a musical example of a space with two open ends
organ pipes or flute
What happens at the ends of a space with one open end and one fixed end?
A node at the fixed end and an antinode at the open end
What is the formula for frequencies with two fixed ends?
Fn = (2n-1)xF1
What is the formula for length of space with two fixed ends?
L = (2n-1)/4 wavelengths
Give a musical example of a space with one fixed and one open end
clarinet
What happens to a pulse at an open end?
Pulse is not inverted
What happens to a pulse at a fixed end?
The pulse is inverted
How is a standing wave usually formed?
A wave is reflected back on itself
Why is it better to measure a standing wave near the reflector?
Energy, and so amplitude, is lost with distance so this is where amplitudes are most similar and the expected interference patterns are seen
