Physics waves basics and polarisation and superposition

Wave defintion

Transfer of energy without the transfer of matter by means of oscillation

What can oscillate to form a wave

Matter or fields

What is the difference between longitudinal waves and transverse waves

Transverse waves oscillate perpendicular to energy transfer, and longitudinal oscillate parallel

Example of longitudinal waves

P-waves, sound

Example of transverse waves

S-waves, light, string

What are the parts of longitudinal waves

Rarefaction and compression

How are the two ways waves can be graphed

Displacement against time or distance

Definition of amplitude

Maximum displacement from rest value

Definition of time period

Time for 1 complete oscillation

Definition of frequency

How many waves pass a point in 1 second

What is superposition

When waves overlap, the resulting wave is the sum of the overlapping waves

What is phase difference

Angle between their wave cycles

Coherence definition

Constant phase difference and same frequency

What happens when 2 identical waves travel in opposite directions

A standing wave is formed with 2 * amplitude

What is path difference

The difference in the distances that 2 waves travel between 2 points

In a stationary wave, what is the phase difference

At an odd number of anti nodes away, out of phase, an even number of anti nodes away is in phase

What is polarisation

Restriction of the oscillation of a wave into 1 plane

Why can longitudinal waves not be polarised

Because they can only vibrate in one direction (can’t be restricted to a plane)

What direction of polarisation passes through a vertical polaroid

A vertical polarisation (opposite polarisations can’t get through the polaroid)

How much unpolarised light gets through a polaroid

The intensity halves

How do sunglasses use polarisation

They have a vertical polaroid, which halves the intensity of light from the sun, and eliminates the horizontally polarised light from reflections so it is easier to see

How do we consider polarised light with microwaves

An antennas oscillating electric field forms vertically polarised light so receiving antenna must be the same direction, A vertical metal grid between the source and receiver will block (horizontal polaroid)

What is an easy way to set up a standing wave

Reflecting a wave back on itself with a string

What are the frequencies of a standing wave called

Resonant frequencies or harmonics

How many nodes are there on the nth harmonic

n+1

What pattern does a tube with powder and a loudspeaker show

there are piles of powders equally spaced at the nodes