Chapter 11 - Waves 1 (pt1)

Question 1

Transverse wave examples

Answer 1

Waves on water surface
EM waves
Waves on a string
S-waves

Question 2

Longitudinal wave examples

Answer 2

Sound waves

P-waves

Question 3

Longitudinal wave diagrams

Answer 3

Show regularly spaced particles and then them moving left and right
Also show the direction of energy transfer
Show compressions and rarefactions

Question 4

Axes on wave profile

Answer 4

y-axis is displacement

x-axis is time

Question 5

Transverse wave

Answer 5

The oscillations are perpendicular to the direction of energy transfer
The wave represents the energy transfer so a particle at any point moves perpendicular to the wave in one direction

Question 6

Longitudinal wave

Answer 6

A wave in which the oscillations are parallel to the energy transfer

Question 7

How does a longitudinal wave work?

Answer 7

Particles vibrate and collide parallel to the wave

Results in areas with many particles (compressions) and areas with few (rarefactions)

Question 8

Progressive wave

Answer 8

A wave in which the oscillations travel through a medium, transferring energy but not matter

Question 9

Displacement

Answer 9

Symbol: s
Unit: m
Definition: The distance from the equilibrium position in a direction of a point on the wave

Question 10

Amplitude

Answer 10

Symbol: A
Unit: m
Definition: Maximum displacement

Question 11

Wavelength

Answer 11

Symbol: λ
Unit: m
Definition: Minimum distance between two adjacent points in phase

Question 12

Period of oscillation

Answer 12

Symbol: T
Unit: s
Definition: The time taken for one oscillation

Question 13

Frequency

Answer 13

Symbol: f
Unit: Hz
Definition: The number of wavelengths passing a point per unit time

Question 14

Wave speed

Answer 14

Symbol: v / c (speed of light. (3x10^8 ms^-1)
Unit: ms^-1
Definition: The distance travelled per unit time

Question 15

Already known equations

Answer 15

f = 1/T
v = fλ

Question 16

Phases of a wave

Answer 16

One full phase is 360° so 2π radians
The phase difference is the angle difference between points in waves of the same frequency at the same displacement
The fraction of the wavelength apart they are is the same as the fraction of 2π

Question 17

Intensity

Answer 17

Power/Area
P/4πr^2 when given a distance, distance is r
The radiant power through a cross-sectional area

Question 18

Intensity ∝

Answer 18

(Amplitude)^2

Question 19

Oscilloscope

Answer 19

Gives you the wave in a visual way (trace) on a grid, the horizontal length of each time box is the time base

Question 20

Frequency from an oscilloscope

Answer 20

1. Read the peak-to-peak distance
2. Multiply by the time base for the period
3. Do 1/T for the frequency

Question 21

Reflection

Answer 21

Wavelength and frequency stay the same
Draw a normal perpendicular to the surface, the angle between the incident ray and the normal is equal to the angle between the reflected ray and the normal

Question 22

What do you draw on a reflection/refraction diagram

Answer 22

A normal

Question 23

Refraction

Answer 23

Light refracts when it moves between mediums
If it enters a denser medium, it slows down, bending towards the normal
Constant frequency, wavelength changes
Draw to show some being reflected on a diagram

Question 24

Diffraction

Answer 24

As waves pass through an aperture (gap) or pass around an obstacle, they will spread out (diffract)
The most diffraction happens if the width of the aperture is closer to the wavelength

Question 25

What happens to water waves as they enter shallower water?

Answer 25

They slow down - shorter wavelength

Question 26

Polarised waves

Answer 26

Transverse waves that only have oscillations in one plane - said to be “plane polarised”

Question 27

Partial polarisation

Answer 27

When there are more waves oscillating in one plane but not exclusively
Happens to reflected waves
E.g. sunlight off a wet road

Question 28

Where is a particle moving from a transverse ray diagram?

Answer 28

Perpendicular to the movement of the wave