Types Of Waves & Polarisation Flashcards
In [……..] waves, vibration is at right angles to the direction of travel.
Transverse
What type of waves are electromagnetic waves?
Transverse waves
Displacement upwards is given a [……..] sign
+ (positive)
What two graphs can waves be drawn on?
Displacement - distance
Displacement - time
In […….] waves the vibrations are along the direction of travel.
Longitudinal
What is the most common example or longitudinal waves?
Sound
What does a sound wave consist of?
Compressions and rarefactions
How do you measure one wavelength on a sound wave?
From 1 compression to another
Compressions and rarefactions create pressure variations - which one creates higher pressure?
Compressions and the molecules are closer together.
Compressions and rarefactions create pressure variations - which on creates lower pressures?
Rarefactions as the molecules are further apart.
What is Reflection?
When the wave is bounced back when it hits a boundary
What is refraction?
The wave changes direction as it enters a different medium.
What is Intensity?
Is the rate of flow of energy per unit area at right angles to the direction of travel of the wave.
What is the Intensity equation?
Intensity = Power / Area
I = P/A
What is intensity proportional to?
Amplitude squared
What do properties do Electromagnetic Waves have in common?
- All EM waves travel in a vacuum at a speed 3 x 10*8 ms-1
- They are transverse waves (consisting of vibrating electric and magnetic fields)
- Can be retracted, reflected and diffracted and undergo interference
- Obey v = f λ
- EM waves carry energy
- They are transverse so can be polarised
When light is reflected it is […….][……]
Partially polarised
How do we know that light is partially polarised when it is reflected from a surface?
If you view the reflected Ray through a polarised filter the intensity of light leaving the filter changes with the orientation of the filter.
Television and radio signals are […..]
Polarised
How are TV signals polarised?
Rods on the aerials polarise the waves through the orientation of these rods on the broadcasting aerial. If the rods on both are not aligned then the signal is weak.
How are Radio Waves polarised?
You are moving the alignment of the rods with a radio as the rods go in and out of alignment.
Why do polarising filters not work on micro waves?
Because their wavelength is too long.
What is used to polarise micro waves?
A metal grille
What equipment do you need to investigate the polarisation of microwaves?
Microwave transmitter
Microwave receiver
Link these to a Voltmeter
