Waves

Question 1

What are waves?

Answer 1

A wave allows energy to be transferred from one point to another some
distance away without any transfer of material between the two points.

Question 2

amplitude

Answer 2

The amplitude of the wave is the maximum displacement of particles from
equilibrium.

Question 3

wavelength

Answer 3

The wavelength of the wave is the distance between adjacent particles
vibrating in phase.

Question 4

frequency

Answer 4

The frequency of the wave, measured in Hertz, is the number of waves
passing a point each second (or the number of waves given out by the source each
second)

Question 5

time period

Answer 5

The time period, T, of the wave is the time it takes one of the wave particles
to do one cycle.

Question 6

Polarised light vs Unpolarised light

Answer 6

Polarised light vibrates in one direction only perpendicular to the direction of
travel of the light.
Unpolarised light vibrates in all directions perpendicular to the direction of
travel of the light.

Question 7

Microwave (grill and polarisation)

Answer 7

The microwaves are polarised in a vertical direction. When the metal grille has its
bars horizontally, the waves pass through and a large signal is detected.
When the bars are vertical then no signal is detected.This is because the microwaves put a force on the electrons in the bars of the grille,
causing them to vibrate. The energy of the microwaves has been absorbed by the
electrons and so the microwave can’t get through the grille.

Question 8

Principle of Superposition

Answer 8

When two waves meet the total displacement at a point is equal to the sum of the
individual displacements at that point

Question 9

Stationary or standing waves are formed when two waves

Answer 9

1. Moving in opposite directions
2. Have the same frequency (and speed)
3. Similar amplitudes
4. Meet and superpose.

Question 10

Nodes

Answer 10

Nodes
The points where the displacement is always zero.
This is where the waves always meet in antiphase and destructively interfere.
There is half a wavelength between nodes.

Question 11

Antinodes

Answer 11

Antinodes
The points where there is maximum amplitude of vibration.
Here the waves meet in phase and constructively interfere.
There is half a wavelength between antinodes.

Question 12

µ

Answer 12

µ is the mass per unit length in kgm-1
μ= mass of the string (kg)/length of the string (m)
l