Ch11: Waves 1 Flashcards
What are the features of a progressive wave?
An oscillation that travels through matter, or a vacuum. And transfers energy but not matter.
What is a transverse wave?
A wave in which the oscillations are perpendicular to the direction of energy transfer.
What is a longitudinal wave?
A wave in which the oscillations are parallel to the direction of energy transfer.
What are some examples of a transverse wave?
Water waves, electromagnetic waves, waves on a stretched spring, s waves from earthquakes.
What are some examples of a longitudinal wave?
Sound waves, P waves in an earthquake
What is displacement in the case of waves?
Distance from equilibrium point, either positive or negative.
What is amplitude of a wave?
Maximum displacement from equilibrium point
What is wavelength of a wave and what is its symbol?
λ. The minimum distance between two in phase points of adjacent waves.
What is the period of oscillation of a wave?
Time taken for a wave to move one wavelength past a given point.
What is the frequency of a wave?
The number of wavelengths passing a given point per unit time.
If a wave has frequency 7 Hz, how many complete oscillations occur a second?
7
How do you find frequency from a period of a wave?
f=1/T T=period
What is phase difference measured in?
Degrees or radians
What is antiphase?
When two waves are at a phase difference of 180° or π radians.
What is the angle between an incident ray and the normal?
Angle of incidence
What is the incident ray?
The line of a ray entering a material.
What is the angle of reflection?
The angle between the normal and the reflected ray.
What happens to wavelength and frequency when a wave is reflected?
They don’t change
When a wave slows down which way does it refract?
Toward the normal
When a wave speeds up which way does it refract?
Away from the normal
What is polarisation of a wave?
When a wave is made to only oscillate in one plane.
How is intensity of a wave defined?
Power per unit area
What is the equation for intensity? Define the terms.
I=P/A
I: intensity
P: power
A: area
What is the relationship between intensity and distance from surface?
Intensity is inversely proportional to r^2. So when distance doubles, intensity reduces by a factor of four.
If distance from the sun increased by 4, what would happen to intensity?
Decrease by a factor of 16.
What is the relationship between intensity and amplitude?
Intensity is directly proportional to amplitude squared.
What are the four properties of a wave?
Transfer energy
Can be refracted
Can be reflected
Can be diffracted
What is one property of a transverse wave, that longitudinal waves do not have?
They can be polarised.
What is the equation for wave speed?
v=λf
How can the v=fλ equation be modified for EM waves?
c=fλ (Because all EM waves travel very close to their speed in a vacuum, which is the same for all EM Waves including light.)
How is refractive index of a material calculated and what is its symbol?
n=c/v
n: refractive index
c: speed of light in a vacuum
v: speed of light in said material
If the refractive index is larger, does it refract toward the normal or away?
Toward the normal - as it is going slower.
What is the equation for the angle between the incident ray and the normal?
nsinθ=k
n= refractive index
k= constant
How can the refractive index equation be used be used for light travelling from one medium to another?
nsinθ(one material)=nsinθ(second material)
What are the two conditions for total internal reflection?
- The ray must be moving from a higher refractive index material into a lower refractive index material.
- The angle it meets the boundary at must be larger than the critical angle.
How is critical angle calculated?
sinC=1/n
What is the relationship between refractive index and critical angle?
Greater the refractive index, n, the lower the critical angle, C.
