4.4 Waves

Question 1

Define term progressive wave

Answer 1

Wave which transfers energy with a wave front which travels through a material

Question 2

What is a transverse wave? And give an example

Answer 2

Particle oscillations are perpendicular to energy propagation
E.g electromagnetic waves

Question 3

What is a longitudinal wave?

Answer 3

Particles oscillate in same direction as energy propagation
Rarefactions= low pressure
Compressions = high pressure

Question 4

Define period and equation

Answer 4

Time taken for one whole wave cycle to be completed
Units : seconds
Period = 1/ frequency

Question 5

Define frequency + equation

Answer 5

Number of wave cycles produced per cycle
Frequency = 1/time period
Units : Hz

Question 6

Define phase difference

Answer 6

Difference in phase of 2 points on a wave or between 2 waves which have the same point or another definition could be the amount at which one wave lags another
Measured in degree or radians

Question 7

Define path difference

Answer 7

Difference in distance travelled by 2 waves from their sources
Measured in terms of wavelength

Question 8

What speed to EM waves travel at in a vacuum?

Answer 8

3.0 x 10 ^8 ms ^-1

Question 9

What type of waves can be polarised?

Answer 9

Transverse waves

Question 10

State the order of the EM spectrum

Answer 10

Radio, micro, infrared, visible light, UV , x-ray , gamma rays
Read my instructions visible under x ray glasses

Question 11

Which EM wave has the longest wavelength and lowest frequency

Answer 11

Radio waves

Question 12

Which EM wave has the shortest wavelength and highest frequency

Answer 12

Gamma rays

Question 13

If speed is constant and the frequency increases then what happens to the wavelength

Answer 13

Decreases as frequency and wavelength are inversely proportional

Question 14

Which EM wave is the most ionising

Answer 14

Gamma rays
Ionisation = electron removed from atom
Causes cancer and kills cells
So is most dangerous

Question 15

State the uses for each EM wave

Answer 15

Radio : radio transmissions
Micro: TV transmissions
Infrared: night vision cameras
Visible light : heat detectors, optical fibres
Uv: security marks
X-rays : bone observation
Gamma rays: kills cancer cells, sterilisation of medical instruments

Question 16

Approximate wavelength of each EM wave

Answer 16

Radio 10 ^3
Micro 10^-2
Infrared 10^-5
Visible light 0.5 x 10^-6
UV 10^-8
X-rays 10^-10
Gamma rays 10^-12

Question 17

Equation for intensity using power and area

Answer 17

Intensity = power /area m²

Question 18

What is the relationship between intensity and amplitude

Answer 18

Intensity is proportional to amplitude squared

Question 19

What equation do you use for intensity and amplitude exam questions?

Answer 19

I/a² = I/a²

Question 20

How do you know where to draw the normal

Answer 20

The normal should always be perpendicular to where the wave meets the boundary

Question 21

State the Law of reflection

Answer 21

Angle of incidence =angle of reflection

Question 22

Dur8ng refraction what happens when a wave enters a denser material

Answer 22

Wavelength decrease and speed of the wave decreases and so bends towards material

Question 23

What is the optical density of a material measured by

Answer 23

Refractive index - ratio of the speed of light to speed of wave through a medium

Question 24

Equation for refractive index (n)

Answer 24

n = c/v where c is constant 3 x 10⁸

Question 25

State snell's law

Answer 25

n x sin theta= n x sin theta

Question 26

What is the critical angle

Answer 26

When a wave is travelling to a more dense material and the angle of refraction is equal to 90 ° which means the wave will refract along the boundary so the critical angle would be the angle that causes this refraction along the boundary.

Question 27

How do you obtain total internal reflection?

Answer 27

When the angle if incidence is greater than the critical angle

Question 28

What is the equation relating the critical angle

Answer 28

Sin C = n2/ n1

Question 29

How does fibre optic Internet work

Answer 29

Infrared waves are sent down a glass/fibre core, as the angle of incidence is greater than the critical angle it is reflected into the glass rather than refracting through.

Question 30

What is the principle of superposition of waves?

Answer 30

When two or more waves cross the resultant displacement is equal to the vector sum of the individual displacements

Question 31

What is the principle of superposition of waves?

Answer 31

When two or more waves cross the resultant displacement is equal to the vector sum of the individual displacements

Question 32

What does constructive interference mean?

Answer 32

Where the individual displacements are both in the same direction and results in a greater resultant displacement

Question 33

What does destructive interference mean?

Answer 33

When the individual displacements are in opposite directions and are 180° out of phase from eachother which means they cancel each other out