UNIT 2 - Nature of Waves

Question 1

What are the two basic types of waves

Answer 1

Transverse and Longitudinal

Question 2

Define transverse waves

Answer 2

Vibrations are 90 degrees to direction of movement

Question 3

Define longitudinal wave

Answer 3

Vibrations are along direction of movement

Question 4

Whats a progressive wave

Answer 4

Transfers energy from one place to another with no net movement of particles/material

Question 5

What are mechanical waves

Answer 5

Waves that travel through a medium

Question 6

3 examples of transverse waves

Answer 6

Water waves
Electromagnetic waves
S-waves (seismic)

Question 7

3 examples of longitudinal waves

Answer 7

Sound waves
Ultrasound waves
P-waves (seismic)

Question 8

Define the amplitude

Answer 8

Maximum displacement of a wave from equilibrium

Symbol (A)
Unit (metres, m)

Question 9

Define wavelength

Answer 9

The distance between adjacent peaks of a wave, (distance between adjacent points on a wave that are in-phase)

Symbol (λ)
Unit (metres, m)

Question 10

Define frequency

Answer 10

Number of wavelengths passing a point per unit time

Symbol (f)
Units (Hertz, Hz)

Question 11

Define Hertz (Hz)

Answer 11

1 Hz is 1 wavelength passing a point per second

Question 12

Define period

Answer 12

Time taken for a wave to make one complete oscilation

Symbol (T)
Unit (seconds, s)

Question 13

Define wave displacement

Answer 13

Distance and direction of a vibrating particle in a wave measured from its undisturbed position

Symbol (y)
Units (metres, m)

Question 14

What does phase mean

Answer 14

The position of a point on a wave in terms of its position in the wave cycle

Question 15

What does in phase mean

Answer 15

2 or more points are vibrating in exactly the same way with same displacement.

Question 16

What does antiphase mean?

Answer 16

When 2 or more points are vibrating exactly out of phase, with exactly opposite displacements.

Question 17

Difference between antiphase and out of phase

Answer 17

Antiphase is when 2 or more points are EXACTLY out of phase

Out of phase is not in phase by some fraction of a wave cycle

Question 18

What is phase angle

Answer 18

Used to show exactly the phase of vibration of particles within a cycle of oscillation. The angle can be measured in either degrees or radians

Question 19

What is phase difference

Answer 19

The amount by which waves are out of phase. Measured in radians or degrees

Question 20

How can waves be created in a water tank

Answer 20

By using a plane dipper or rod dipper vibrating on the surface of water in a tank

Question 21

What are wavefronts

Answer 21

The straight or circular lines which travels away from the source of the waves

All points along the wave front are therefore oscillating in phase

Question 22

How is the direction of propagation shown

Answer 22

With a line which is at right angles to the wavefront

Question 23

What is wave velocity

Answer 23

Wave velocity = frequency x wavelength

V = f x λ

Question 24

What is a plane polarised wave

Answer 24

A wave is plane polarised if the particles or electromagnetic field oscillates in a single plane. This is a property of transverse waves.

Question 25

What is polarisation

Answer 25

Process of turning an unpolarised wave into a plane polarised wave through the use of a polarising filter

Question 26

How does polarisation work (1 filter)

Answer 26

The polarising filter lets light with the same plane of polarisation through, and all other waves are absorbed.

Eg. Vertical oriented polarising filter will let through the light oscillating in the vertical direction, and all other waves get absorbed

Question 27

How does polarisation work with 2 polarising filters 90 degrees to eachother?

Answer 27

the first polariser will let through the light with same plane of polarisation only and absorb the rest of the waves, and then the second polariser absorbs the light that was let through because it is oriented 90 degrees to the first polariser. So no light is let through.

0 intensity
I = 0

Question 28

What is an unpolarised wave

Answer 28

Vibrations in many planes

Question 29

What happens if light goes through two polarisers of the same plane as each other are used

Answer 29

The polarisers are same orientation so the light that oscillates in the same plane as the polarisers will pass through both. There will be a plane polarised eave transmitted with maximum intensity.

Imax

Question 30

What happens to light if it passes through a vertically oriented polariser and a second polariser rotated at an angle θ

Answer 30

The light with same plane of polarisation goes through the first polariser, then some of it will pass through the second rotated polariser because its at an angle What happens to light if it passes through a vertically oriented polariser and a second polariser rotated at an angle θ

Intensity is reduced

Question 31

What is malus’ law

Answer 31

I=Imax cos² θ

THIS IS GIVEN so ye idk

Question 32

List 2 practical uses of polarisation

Answer 32

1. Used in sunglasses to reduce intensity of light
2. 3D cinema glasses, one lenses is verticle plane, other lenses is horizontal plane.

Question 33

Define diffraction

Answer 33

The spreading out of waves when they meet obstacles such as the edges of a slit. Some of the waves energy travels into geometrical shadows of the obstacles