Diffraction & Polarisation Flashcards
What is polarisation?
The process by which the direction of vibrations of the rays of light is restricted. All the waves are transverse.
What is diffraction?
The Bending of waves around obstacles
What happens the light diffracts through a small slit?
It creates parallel bands of light
What are the the bright bands an example of?
Constructive interference
What are dark fringes called?
Destructive Interference
Why can’t the longitudinal waves be polarised?
Bc in long. waves, the direction of propagation is parallel to the particle oscillation, hence only existing in one plane. Polarisation must occur when perp. in order to be polarised.
What is unpolarised light?
Consists of EM waves that are oscillating in multiple planes.
Suggest an example of unpolarised light.
Light from the sun or a lightbulb
What is polarised light?
EM waves oscillating in one plane.
Describe the process of polarisation.
The light waves pass through a polarizer, a stretched plastic that is aligned in the direction, which only enables the light oscillating in that specific plane to go through.
What occurs on the first polariser?
We have to resolve into components hence the unpolarized light halves the intensity.
Imax = I/2
What is the first filter known as?
Polariser
What is the second filter known as?
Analyser
What do you have to memorise abt the intensity of light?
Intensity of light is proportional to the square of the amplitude.
What is Malus’s Law?
I = Imax cos^2(theta)
