Waves

Question 1

What are Mechanical Waves?

Answer 1

Waves where energy is transferred through a medium

Question 2

What are Progressive Waves?

Answer 2

Waves which transfer energy as a result of oscillations of the medium through which the energy is travelling

Question 3

What are Longitudinal Waves?

Answer 3

Waves whose oscillations are parallel to the direction of energy transfer

Question 4

What are Transverse Waves?

Answer 4

Waves whose oscillations are perpendicular to the direction of energy transfer

Question 5

What is Wavelength?

Answer 5

Distance a wave travels as it completes one full wave cycle

Can be measured by the difference in distance for corresponding points on consecutive wave cycles

Question 6

What is Frequency?

Answer 6

Number of Wavelengths passing through a point in a period of time

(Inversely proportional to the Time Period)

Question 7

What is the Time Period?

Answer 7

Time taken for one complete wavelength to pass a certain point

(Inversely proportional to Frequency)

Question 8

What is Wave Speed?
What is the Wave Equation?

Answer 8

The distance a wave travels in a period of time

v = fλ

Question 9

What is Displacement?

Answer 9

The distance moved from the equilibrium for a point on a wave

Question 10

What is Amplitude?

Answer 10

Maximum displacement from the equilibrium

Question 11

What is Phase Difference?

Answer 11

The angle seperating two points on a wave cycle

Question 12

What are the conditions of Phase Difference for waves to be ‘In-Phase’, ‘in Anti-phase’ & ‘out of Phase’?

Answer 12

In-Phase = 2n(180’)
Anti-phase = n(180’)
(where n is a whole number)
Out of Phase = anything else

Question 13

What is Path Difference?

Answer 13

Distance seperating two points along a wave cycle

Question 14

What are the conditions of Path Difference for waves to be ‘In-Phase’, ‘in Anti-phase’ & ‘out of Phase’?

Answer 14

In-phase = nλ
Anti-phase = (n + 0.5)λ
(where n is a whole number)
Out of Phase = anything else

Question 15

How do you convert Radians to Degrees?

Answer 15

Rad. x (180/π)

Question 16

How do you convert Degrees to Radians?

Answer 16

Deg. x (π/180)

Question 17

How many radians in a full wave cycle?

Answer 17

2π radians

Question 18

How many degrees in a full wave cycle?

Answer 18

360 degrees

Question 19

What are the 4 ways a wave can be impacted by its surroundings?

Answer 19

Reflection - Wave changes direction at a boundary between two media (remaining within original medium)

Refraction - Changes direction of Light as it transitions from one medium to another - due to change in speed of travel

Diffraction - When a wave moves through a slit, the wave spreads out after passing through the gap

Polarisation - When light is restricted to oscillating in a single plane

Question 20

What is Intensity?

Answer 20

The radiant power transferred per unit Area

Question 21

What is the relation between Wave Intensity and Amplitude?

Answer 21

Intensity is directly proportional to Amplitude squared

Question 22

What is an Electromagnetic Wave?

Answer 22

Transverse Waves created when an Electric Field and Magnetic Field couple together

They do not need a medium to oscillate in

Question 23

What is the order of the EM Spectrum?

Answer 23

Radio, Micro, Infrared, Visible, UV, X-ray, Gamma

Question 24

What is the range of wavelengths and frequencies for Radio Waves?

Answer 24

> 10^-1 m
<3x10^9 Hz

Question 25

What is the range of wavelengths and frequencies for Microwaves?

Answer 25

10^-1 - 10^-3 m
3x10^9 - 3x10^11 Hz

Question 26

What is the range of wavelengths and frequencies for Infrared Radiation?

Answer 26

10^-3 - 7x10^-7 m
3x10^11 - 4x10^14 Hz

Question 27

What is the range of wavelengths and frequencies for Visible Light?

Answer 27

7.8 - 3.9 x 10^-7 m
4.0 - 7.5 x 10^14 Hz

Question 28

What is the range of wavelengths and frequencies for UV Light?

Answer 28

3.9x10^-7 - 10^-8 m
10^16 - 10^18 Hz

Question 29

What is the range of wavelengths and frequencies for X-Rays?

Answer 29

10^-8 - 10^-12 m
10^18 - 10^20 Hz

Question 30

What is the range of wavelengths and frequencies for Gamma Rays?

Answer 30

<10^-12 m
>10^20 Hz

Question 31

What is Polarisation?

Answer 31

When a transverse wave is filtered so that is oscillates in a single plane

Question 32

What happens when a light travels through two parallel polarising filters?

Answer 32

The light will simply be Plane Polarised - passing through the second filter without any changes

Question 33

What happens when a light travels through two perpendicular polarising filters?

Answer 33

No light will be able to pass through the second filter

(First filter polarises light to a single plane, which is then blocked by the second filter)

Question 34

What is the Refractive Index of a medium?

Answer 34

The ratio between Speed of Light in a Vacuum and the Speed of Light in the medium

n = c / v

Question 35

What is Snell’s Law?

Answer 35

n1.sinΘ1 = n2.sinΘ2

Question 36

What happens to the Speed of Light as it enters a medium with a higher refractive index?

Answer 36

Light slows down and angles towards the normal

Question 37

What happens to the Speed of Light as it enters a medium with a lower refractive index?

Answer 37

Light speeds up and angles away from the normal

Question 38

What is the Critical angle of a medium?

Answer 38

The angle of incidence at the boundary between two media that will produce an angle of refraction of 90’ from the normal.
(Run along the boundary of the medium)

Question 39

What is the equation for the Critical Angle?

Answer 39

Sin C = n2 / n1

Question 40

What is Total Internal Reflection?

Answer 40

The reflection of all light back into the original medium when hitting a boundary between two media

Question 41

What are the stipulations for Total Internal Reflection?

Answer 41

The original medium will have a higher refractive index and the angle of incidence must be greater than the Critical Angle