Chapter 4 - Waves #1

Question 1

What are mechanical waves?

Answer 1

Waves that travel through a medium.

i.e. oscillations of matter.

Question 2

Electromagnetic waves are…

Answer 2

… oscillating electric and magnetic fields that pass through space without the need for a medium.

Question 3

Electromagnetic waves include…

Answer 3

Radio waves, microwaves, infrared radiation, X-rays and gamma radiation

Question 4

What are longitudinal waves?

Answer 4

Waves in which the direction of vibration of the particles is parallel to the direction in which the energy travels.
Longitudinal waves consist of regions of compression and rarefaction.

Question 5

What are transverse waves?

Answer 5

Waves in which the direction of vibration is perpendicular to the direction in which the wave travels (direction of energy transfer).

Question 6

What are plane-polarised waves?

Can longitudinal waves be polarised?

Answer 6

Transverse waves that vibrate in one plane only.

Longitudinal waves cannot be polarised.

Question 7

What is the displacement of a vibrating particle?

Answer 7

Its distance and direction from its equilibrium position.

Question 8

What is the amplitude of a wave?

Answer 8

The maximum displacement of a vibrating particle.

Question 9

What is the wavelength of a wave?

Answer 9

The least distance between two vibrating particles with the same displacement and velocity at the same time. (e.g. distance between adjacent peaks).

Question 10

One complete cycle of a wave is…

Answer 10

From the maximum displacement to the next maximum displacement. (e.g. from one wave peak to the next).

Question 11

What is the period of a wave?

Answer 11

The time for one complete cycle to pass a fixed point.

Question 12

What is the frequency of a wave?

Answer 12

The number of complete cycles passing a point per second.

Question 13

What are the values for 1 cycle.

Answer 13

360°

2π

Question 14

How do you calculate phase difference in radians?

Answer 14

  λ

Question 15

Give two examples of longitudinal waves.

Answer 15

Sound waves

Primary seismic waves

Question 16

Give three examples of transverse waves.

Answer 16

Electromagnetic waves
Secondary seismic waves
Waves on a string

Question 17

What is an oscillation?

Answer 17

A periodic vibration about an equilibrium.

Question 18

If two points oscillating at the same _______ reach their maximum positive or negative displacement at the same time, they are said to _______ __ ______.

Answer 18

If two points oscillating at the same frequency reach their maximum positive or negative displacement at the same time, they are said to oscillate in phase.

Question 19

If one point reaches maximum positive displacement as another reaches maximum negative displacement, the points ______ __ ________.

Answer 19

If one point reaches maximum positive displacement as another reaches maximum negative displacement, the points oscillate in antiphase.

Question 20

If polarised light is passed through a polaroid filter that is perpendicular to the plane of polarisation of the polarised light…

Answer 20

…no light will get through.

Question 21

Give 2 applications of polarisers.

Answer 21

• Polaroid material (e.g. sunglasses)

- Alignment of aerials for transmission and reception

Question 22

What is the ‘direction of propagation’?

Answer 22

The direction in which a wave travels.

Question 23

Polarisation is evidence that electromagnetic waves are…

Answer 23

…transverse