Reflection Refraction Diffraction And Polarisation Flashcards
Alll… Waves can be ….
Progressive
Reflected, refracted and diffracted
When does reflection occurs
When a wave changes direction at a boundary between two media, remaining in the original medium.
The angle of incident is measured from the
Normal of the the medium
When does refraction occurs
When a wave changes direction as it changes speed, i.e. changes medium. In changing medium the frequency of the wave remains constant. Hence the wavelength changes as a result. Moreover the will always be some partial reflection at the boundary between two media
Sound wave speed up in … materials
Denser
EM waves slow down in…materials
Denser
When does diffraction occurs
Is the spreading out of a wave front as it passes through a gap. The wavelength and frequency of the wave are not altered.
When does maximum diffraction occurs
When the gap the wave passes through is the same size as the wavelength of the incident wave.
Polarisation
A property unique to transverse waves. It is when the oscillation of a wave are restricted to one place only, hence, the wave is said to be plain polarised. In other words is the attenuation of transverse waves oscillating in a particular orientation
Why can’t longitudinal waves not be polarised
The direction of energy transfer is already in one plane only, whereas in transverse waves, the oscillations occur in many places at right angles to the direction of travel.
Intensity of a progressive wave wave is defined as
The radiant power passing at right angles through a surface per unit area
I=P/A (Wm^-2)
As light spreads out in a sphere the area can be taken as the area of sphere.
Therefore intensity is proportional to amplitude squared
EM waves
Are transverse progressive waves consisting of magnetic and electric fields that oscillate at right angles to each other. They can travel through a vacuum at the speed of light c
Refraction of light equation
n=c/v where n is the refractive index and can be used to determine the angle of refraction in to the medium
Angle of refraction equation
n1sin@1=n2sin@2
When does total internal reflection happens
When the light is travelling from a material with a higher refractive index to a material of lower refractive index and the angle of incidence must be above the critical angle
