Waves Flashcards
What is a progressive wave?
an oscillation that travels through space transmitting energy from one place to another
In what direction are the oscillations to the direction of energy transfer in transverse waves?
perpendicular
In what direction are the oscillations to the direction of energy transfer in longitudinal waves?
parallel
Define displacement:
the distance from the equilibrium position in a particular direction
Define amplitude:
the maximum displacement of a wave
Define wavelength:
the distance between 2 adjacent points on a wave that are oscillating in phase
Define period:
the time taken for the wave to move a distance of one whole wavelength
Define frequency:
the number of wavelengths passing through a point per unit time
Define wave speed:
distance travelled by wave per unit time
What is the relationship between period and frequency?
f=(1/T)
What is phase difference?
the fraction of an oscillation between two oscillating particles
What is the phase difference of 1 wavelength?
2π
When does reflection occur?
when a wave changes direction at a boundary between two different media, remaining in the original medium
When does refraction occur?
when a wave changes direction as it changes speed when it passes from one medium to another
What is diffraction?
the spreading of a wave when it passes through a narrow gap or around an obstacle
Within reflection what are the incident and reflected waves always in the same?
plane
Within reflection what things are equal to each other?
angle of incidence and reflection
Within refraction what remains constant?
frequency of the refracted waves
What changes within refraction?
the speed and therefore wavelength of the refracted wave
What does not change within diffraction?
speed, wavelength and frequency
When is there significant diffraction?
width of the gap is similar to the wavelength of the incident wave
Where does a plane polarised wave oscillate?
in one plane only
How can you plane polarise light?
pass it through a polarised filter
Define intensity:
the radiant power passing at right angles through a surface per unit area
Why does intensity from a point source of power P decrease with distance from the source?
the power spreads over a larger surface area
What is intensity directly proportional to?
amplitude squared
Which type of EM waves have the shortest wavelength?
gamma waves
Which type of EM waves have the longest wavelength?
radio waves
What can all EM waves travel through?
a vacuum
What is the speed of EM waves?
3 x 10^8
What type of wave are EM waves?
transverse
What do all EM waves consist of?
oscillating magnetic and electric fields at right angles to each other
How do you produce plane polarised waves with the electric field oscillating in the vertical plane?
pass microwaves from a microwaves transmitter through a metal grill towards a microwave receiver
When polarising microwaves what happens when the metal grille is horizontal?
vertical plane polarised waves are transmitted through
When polarising microwaves what happens when the metal grille is vertical?
vertically plane polarised waves are absorbed by the free electrons within the metal rods of the grille therefore there is almost no transmission
Define refractive index:
speed of light in a vacuum divided by the speed of light in the material (c/v)
What is the law of refraction?
n1sin1=n2sin2
When is there no refraction?
when total internal refraction of the light occurs at the boundary between 2 transparent materials
What happens when there is no refraction due to total internal reflection?
all energy of the wave is returned back into the material
When does total internal reflection take place?
- light in the material travels towards a material with lower refractive index
- angle of incidence is greater than the critical angle
When does a critical angle occur?
when the angle of refraction is 90 degrees
