Waves - Basics - Chapter 15 Flashcards
What is a progressive wave?
A wave that carries energy from one place to another.
What is the position that an oscillation vibrates about?
The equilibrium position or mean position.
What is a mechanical wave?
A wave that travels through a medium.
SUD of wavelength?
S - lambda
U - m
D - the distance between two adjacent points that are in phase.
SUD of period?
S - T
U - s
D - time taken for one complete oscillation of a point in a wave.o
SUD of frequency?
S - f
U - Hz (seconds power -1)
D - the number of oscillations of a particle per unit time.
SUD of displacement?
S - x bar (mean of x)
U - m
D - distance of any part of the wave from the mean position (can be + or -).
SUD of amplitude?
S - A
U - m
D - the maximum displacement of a wave from it’s mean position (positive only).
SUD of phase difference?
S - O with a line through it
U - rad
D - the fraction of a cycle between the oscillations of two particles, expressed in degrees.
Define intensity?
The power transmitted normally through a surface per unit area.
Intensity equation?
I = power/unit area
(w/m2) = (W)/(m2)
I is proportional to the square of the amplitude (inverse square law).
What is a pure wave?
Smooth wave, no jagged edges.
What is a regular wave?
Set wavelength and set amplitude.
Power = ?
E(J) / t(s).
Examples of transverse waves?
Water waves, s-waves, EM waves.
What is a transverse wave?
A wave where the displacement is perpendicular to the direction of the wave.
What is a longitudinal wave?
A wave where the displacement is parallel to the direction of the wave (pressure waves).
Examples of a longitudinal wave?
Sound waves, p-waves, wind instrument.
What is an impure wave?
A wave with jagged edges.
What is an irregular wave?
A wave with a random line (unpredictable amplitude and wavelength).
When measuring phase difference, what is 360 degrees?
2pi radians
What is 180degrees when measuring phase difference?
1pi radians
Speed of a wave = ?
Frequency (1/time) x wavelength
f x lambda
What is path difference?
The difference in the distances travelled by two waves from coherent sources at a particular point.
Define refraction?
The change in direction of a wave as it crosses an interface between two materials where it’s speed changes. Frequency doesn’t change!
Intensity equation 2?
Intensity=
Power / cross sectional area
What is speed of propagation, and if it changes how is this shown on a displacement position graph?
It is the speed at which a wavefront passes through a medium, relative to the speed of light.
It will not affect a displacement position graph?
Define diffraction?
The spreading of a wave when it passes through a gap or past the edge of an object.
Define reflection?
The bouncing back of a wave from a surface.
Define coherent?
Two sources are coherent when they emit waves with a constant phase difference.
Define antinode?
A point on a stationary wave with maximum amplitude.
Define dispersion?
The splitting of light into its different wavelengths.
Define electromagnetic spectrum?
A family of waves that travel through a vacuum at a speed of 3.0x10^8 m/s.
Define power?
The rate at which energy is transferred or the rate at which work is done.
Define rarefaction?
A region in a sound wave where the air pressure is less than the mean value.
Define wave?
A periodic disturbance travelling through space, characterised by vibrating particles.
How are water waves refracted?
Water waves are refracted when the depth of the water changes. Shallower water means the waves travel slower than deeper water.
Page 165?
Diagram on reflection.
How high frequencies can the human ear detect?
20Hz to 20kHz
Angle of reflection =
Angle of incidence
