Waves

Question 1

Progressive wave

Answer 1

A wave that transfers energy without transferring material and is made up of particles of a medium oscillating

Question 2

Amplitude

Answer 2

A wave’s maximum displacement from the equilibrium position

Question 3

Frequency

Answer 3

The number of complete oscillations passing through a point per second

Question 4

Wavelength

Answer 4

The length of one whole oscillation

Question 5

Speed

Answer 5

The distance travelled by the wave per unit time

Question 6

Phase

Answer 6

The position of a certain point on a wave cycle

Question 7

Phase difference

Answer 7

How much a particle/wave lags behind another particle/wave

Question 8

Period

Answer 8

Time taken for one full oscillation

Question 9

What happens when 2 points on a wave are in phase?

Answer 9

Two points on a wave are in phase if they are both at the same point of the wave cycle, they will have the same displacement and velocity and their phase difference will be a multiple of 360 degrees. They do not need the same amplitude, only the same frequency and wavelength.

Question 10

What happens when 2 points on a wave are completely out of phase?

Answer 10

Two points on a wave are completely out of phase when they’re an odd integer of half cycles apart

Question 11

Transverse waves

Answer 11

Oscillation of particles is at right angles to the direction of energy transfer e.g. EM waves which travel at 3x10^8 ms^-1

Question 12

Longitudinal waves

Answer 12

Oscillation of particles is parallel to the direction of energy transfer

Question 13

Polarised waves

Answer 13

A polarised wave oscillates only in one plane and only transverse waves can be polarised. Polaroid sunglasses are an application of polarisation.

Question 14

Superposition

Answer 14

Superposition is where the displacements of two waves are combined as they pass each other, the resultant displacement is the vector sum of each wave’s displacement.

Question 15

Constructive interference

Answer 15

Constructive interference occurs when 2 waves have displacement in the same direction

Question 16

Destructive interference

Answer 16

Destructive interference occurs when one waves has positive displacement and the other has negative displacement, if the waves have equal but opposite displacements, total destructive interference occurs.

Question 17

Stationary wave

Answer 17

A stationary wave is formed from the superposition of 2 progressive waves, travelling in opposite directions in the same plane, with the same frequency, wavelength and amplitude. No energy is transferred by a stationary wave.

Question 18

Antinodes

Answer 18

Where the waves meet in phase, constructive interference occurs so antinodes are formed, which are regions of maximum amplitude.

Question 19

Nodes

Answer 19

Where the waves meet completely out of phase, destructive interference occurs and nodes are formed, which are regions of no displacement

Question 20

Path difference

Answer 20

The difference in the distance travelled by two waves

Question 21

Coherent light source

Answer 21

A coherent light source has the same frequency and wavelength and a fixed phase difference.