(3.1) - Progressive and Stationary Waves

Question 1

Amplitude

Answer 1

The maximum displacement of a wave from its equilibrium

Question 2

Frequency

Answer 2

The number of complete wave cycles that pass a given point in one second

Question 3

Wavelength

Answer 3

The distance between two consecutive points that are in phase on a wave

Question 4

Speed

Answer 4

The rate at which a wave travels through a medium

Question 5

Phase

Answer 5

The position of a point within one complete cycle of a wave

Question 6

In phase, Out of phase, Anti phase

Phase difference in Stationary wave

Answer 6

• In phase: every particle between 2 nodes
• Out of phase: Doesn’t exist
• Antiphase: Every particle in adjacent nodes

Question 8

Stationary wave phase difference rule:

Answer 8

• If particles are seperated by an odd number of nodes, they are pi out of phase (180 degrees)
• If particles are seperated by an even number of nodes, they are in phase (0 degrees)

Question 9

Definition, properties, and examples

Longitudinal Waves

Answer 9

1. Oscillates parallel to direction of wave travel
2. Compressions and rarefractions
3. Sound waves, seismic P

Question 10

Definition, properties, and examples

Transverse Waves

Answer 10

1. Oscillates perpendicular to the direction of wave travel
2. Oscillates in crests and troughs
3. Waves on a string, seismic S

Question 11

Polarised wave

Answer 11

Wave which only oscillates in one plane

Question 12

Why can’t longitudinal waves be polarised

Answer 12

They only oscillate in one plane (parallel) constantly

Question 13

Uses of polarisation

Answer 13

• TV and radio signals
• Sunglasses

Question 14

How they work, and examples:

Polarisation in Alignment of Aerials for Transmission and Reception

Answer 14

• Transmitted waves from towers are recieved from antenna. Antenna must be alligned with polarised waves from tower for max strength
• Examples are Tv and Radio

Question 15

What is a stationary wave?

Answer 15

Two waves with same frequency and amplitude travel in opposite directions and superpose with each other

Question 16

What is a node?

Answer 16

Region on stationary wave with no vibrations

Question 17

What is an antinode?

Answer 17

Region on stationary wave where vibrations are at maximum amplitude

Question 18

Superposition

Answer 18

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

Question 19

‘In phase’

Answer 19

Two waves that:
* have the same frequency
* are at the same point in their cycles

Question 20

‘Anti-phase’

Answer 20

Two waves that both:
* Have the same frequency
* Have a phase difference of 180 degrees

Question 21

‘Out of phase’

Answer 21

Two waves have any phases difference, except 0, and any multiple of 180 degrees

Question 22

Constructive interference

Answer 22

2 waves with same frequency and amplitude are in phase, and their amplitudes combine

Question 23

Destructive interference

Answer 23

2 waves with same frequency and amplitude are anti-phase, and their amplitudes combine

Question 24

How does a stationary wave on a string form?

Answer 24

1. Wave reflects off fixed end and superposes with itself.
2. First harmonic has 2 nodes and 1 anti-node

Question 25

How does a stationary wave using a microwave form?

Answer 25

1. A microwave source reflects off a metal plate, and forms a stationary wave. 2. Microwave probe can detect nodes and anti-nodes

Question 26

How does a stationary wave in sound waves form?

Answer 26

1. Using a loudspeaker inside a closed column creates sound waves. 2. This can be demonstrated by placing fine powder inside the column; at certain frequencies, it gathers at nodes, showing zero disturbance.

Question 27

Phase difference = Path difference equation

Answer 27

Δϕ = 2πd / λ