Polarisation Flashcards
What do polarising lenses do?
Polarising lenses reduce glare.
What are features of EM waves?
All EM waves are transverse and have the same speed of propagation, c, in empty space.
What is the wavelength range for radio waves?
Wavelength range = 10^6m to 10^-1m
What is the wavelength range for microwaves?
10^-1 to 10^-3 m
What is the wavelength range for infrared?
10^-3 to 7*10^-7
What is the wavelength range for visible light?
710^-7 - 410^-7 m
What is the wavelength range for UV?
4*10^-7 to 10^-8m
What is the wavelength range for X-Rays?
10^-8 to 10^-10m
What is the range for gamma rays?
10^-13m to 10^-16 m
How do transverse waves vibrate?
Polarised waves vibrate in one plane only, whereas unpolarised waves vibrate in randomly changing planes. Magnetic fields vibrate in one direction and electric fields in another.
How do polarising filters work?
Polarising filters cut out the planes vibrating perpendicular to it, reducing the amount of light which passes through. Intensity changes using a filter.
How can polarisation of radiowaves in space be proven?
Rotate a receiving aerial to see if intensity changes.
What is the milk water experiment?
Shine a narrow beam of light through water with a few drops of milk. Look through a polarising filter at light scattering up and rotate it slowly, showing the light to be polarised. This can also be done using microwaves and a grille. Rotate the grille between the transmitter and receiver.
