Section 3: Waves

Question 1

What is a progressive wave?

Answer 1

Carries energy from one place to another without transfering any material.

Question 2

What causes a wave?

Answer 2

Somthing making particles or fields osscillate at a source.

Question 3

What is reflection?

Answer 3

The wave is bounced back when it hits a boudary.

Question 4

What is Refraction?

Answer 4

When the wave changes direction as it enters a different medium. The change in direction is a result of the wave slowing down or speeding up.

Question 5

What is diffraction?

Answer 5

When a wave spreads out as it passes through a gap, or a round an obsicle.

Question 6

What is displacment in terms of waves?

Answer 6

How far a point on the wave has moved from it’s undisturbed position.

Question 7

What is amplitude?

Answer 7

The maximum magnitude of the displacement.

Question 8

What is wavelength?

Answer 8

The length of one whole wave oscillation.

Question 9

What is a period?

Answer 9

The time taken for one whole wave cycle.

Question 10

What is the frequency?

Answer 10

The number of whole wave cycles per second passing a given point.

Question 11

What is Phase?

Answer 11

A measurment of the position of a certain point along the wave cycle.

Question 12

What is Phase difference?

Answer 12

The difference in phase between two points on a wave, radians

Question 13

What is the speed of light in a vacume?

Answer 13

3 X 10^8 m/s

Question 14

What is the speed of a sound wave?

Answer 14

Around 340 m/s

Question 15

What is a polarised wave?

Answer 15

A wave that oscillates in one direction only.

Question 16

What is the principle of superposition?

Answer 16

When two or more waves cross, the resultant displacment equals the vector sum of the individual displacements.

Question 17

When does constructive interference occur?

Answer 17

When a trough meets another trough and peak meets peak.

Question 18

When does deconstructive interference occur?

Answer 18

When a crest meets a trough.

Question 19

Investigating resonant frequencys , what equitment is used?

Answer 19

signal generator
vibration transducer
string
pulley
mass

Question 20

Investigating resonant frequencys, what do you do?

Answer 20

Find the first harmonic (a single anode and has a node at each end)
note the frequecy, keep everything the same appart from the distance between the pully and transductor

Question 21

When will an emerging light ray from a semi-circular block not its change direction as it levels the block?

Answer 21

• Internal ray is a radius
  -internal ray travels along the normal
  -ray meets (glass - air) boundary at ninty degrees
  -angle of incidence is zero

Question 22

A circuit is set up to determine the emf and internal resistance of a cell.
it has a fixed and variable resistor in it.
explain why the studet used the fixed resistor?

Answer 22

• to limit (maximum) current when variable resistor is set to zero
  -to prevent overheating /damage to cell
• otherwise cell would discharge quickly

Question 23

On a voltage/pd current graph what does the gradient give?

Answer 23

Resistance

Question 24

Is a smaller or bigger core better for a greater pulse transmission rate?

Answer 24

• smaller diameter
• greater rates occur when pulses are shorter in time , there is less modal dispersion
• smaller diameter = less modal dispersion = smaller range of path lengths

Question 25

Is impules a vector of scalar force?

Answer 25

Vector

Question 26

List the order of Em waves from longest wave length to shortest. 7

Answer 26

Radio Micro Infrared Visible Ultraviolet X-ray Gamma ray

Question 27

What is material dispersion?

Answer 27

Waves of different wavelengths travel at slightly different speeds theough an optic fibre and so reach the end of the fiber at slighlty different times, causing pulse broadening.

Question 28

What is modal dispersion?

Answer 28

Waves enter an optical fibre at slightly different angles, meaning the distance each beam has to travel is slightly different. This leads to the beams reaching the end at different times and so cause pulse broardening.

Question 29

What is Snell’s law?

Answer 29

A law linking a wave’s angle of incidence to its angle of refraction, with the use of the refractive indexes of the mediums involved.

Question 30

How are stationary waves formed?

Answer 30

Stationary waves are produced by the superposition of two waves of the same frequency and amplitude travelling in opposite directions

Question 31

Diffraction grattings how do you calculate number of lines per meter

Answer 31

N=1/d d= distance between spaces

Question 32

Diffraction gratings is one light has a longer wavelength than another how do the apperence of their maximas differ?

Answer 32

The longer wavelength the wider spaced the maxima are.

Question 33

When does total internal refraction occur?

Answer 33

When the angle of incidence is greater than the critical ange

Question 34

Why is there a negative sight in the a=-w^2x equation

Answer 34

The displacment is in the opposite direction to the acceleration vector.

Question 35

State the 2 condidtions neecessary for an object to be in simple harmonic motion.

Answer 35

-The objects acceleration is proportional to its displacment from the equlibrium position -This acceleration is directed towards the equilibrium position.

Question 36

Antinode: ​

Answer 36

A position of maximum displacement in a stationary wave.

Question 37

Coherence:

Answer 37

​Waves are coherent if they have the same wavelength and frequency, as well as there being a fixed phase difference between them.

Question 38

Electromagnetic Waves: ​

Answer 38

Waves that consist of perpendicular electric and magnetic oscillations.

Question 39

Path Difference:

Answer 39

A measure of how far ahead a wave is compared to another wave, usually expressed in terms of the wavelength.

Question 40

Pulse Broadening: ​

Answer 40

The elongation of a signal passed down an optical fibre, commonly due to modal or material dispersion.

Question 41

Refractive Index: ​

Answer 41

A material property that is equal to the ratio between the speed of light in a vacuum, and the speed of light in a given material.

Question 42

Stationary Wave: ​

Answer 42

A wave that stores, but does not transfer, energy.

Question 43

D sin()=nx wavelength, What does d stand for?

Answer 43

slit spacing

Question 44

Does red light have a longer or shorter wave length than blue light?

Answer 44

longert wave length

Question 45

When is d sin(theta) = wavelength x n vaild?

Answer 45

If the slit-screen distance is a lot greater than the slit seperation.