Chapter 12: Waves 2

Question 1

what is superposition?

Answer 1

when two waves overlap at a point in space

Question 2

Principle of Superposition

Answer 2

“when two or more waves cross, the resultant displacement equals to the vector sum of the individual displacements”

Question 3

Constructive Interference

Answer 3

if both waves are travelling in the same direction, the displacement combines into one big wave

Question 4

Destructive Interference

Answer 4

when the waves are travelling in opposite directions and their displacements cancel out, waves are in antiphase

Question 5

What does an increase in amplitude in constructive interference lead to?

Answer 5

increase in intensity
intensity is directly proportional to (amplitude)2

Question 6

What is Interference

Answer 6

when two or more waves propagating in the same medium meet at a point

Question 7

What do interference patterns consists of?

Answer 7

maxima and minima

Question 8

How do you create a stable interference pattern?

Answer 8

use coherent waves

Question 9

Coherence

Answer 9

waves emitted from two sources having a constant phase difference, must have the same frequency

Question 10

What are maxima and minima both the results of?

Answer 10

result of two waves having travelled different distances from their source

Question 11

path difference

Answer 11

difference in distance travelled by two waves from their sources to the point where they meet

Question 12

What happens when the path difference is a whole number of wavelengths?

Answer 12

constructive interference

Question 13

What happens when the path difference is a whole number AND A HALF of wavelengths?

Answer 13

destructive interference
(n + ½)λ

Question 14

what is the central maxima?

Answer 14

a point where the path difference AND phase difference are both 0º

Question 15

what is first order maxima?

Answer 15

path difference is one whole wavelength, phase difference is 360º, constructive interference occurs

Question 16

what is first order minima?

Answer 16

path difference is half a wavelength. Phase difference of 180º, destructive interference occurs

Question 17

phase difference

Answer 17

the difference in phase between two waves that arrive at the same point
measured in radians or degrees

Question 18

what is needed to form an interference pattern?

Answer 18

two coherent waves

Question 19

monochromatic light

Answer 19

single wavelength, single colour

Question 20

what equipment is involved in Young’s double slit experiment

Answer 20

monochromatic light
narrow slit

Question 21

What varies with the frequency of light used in Young’s Experiment

Answer 21

the distance between the maxima and the minima

Question 22

what is the double slit equation

Answer 22

wavelength = distance between slits x width between maxima / distance from slit to the screen

Question 23

when can you use the double slit equation?

Answer 23

when a < D

Question 24

How are stationary waves produced?

Answer 24

superposition of two waves of the same frequency and amplitude travelling in opposite directions

Question 25

what does a stationary wave look like?

Answer 25

peaks and troughs do not seem to move

Question 26

how are stationary waves different to regular waves?

Answer 26

it stores energy instead of transferring it

Question 27

Fundamental frequency

Answer 27

frequency of the fundamental mode of vibration

Question 28

node

Answer 28

a region where there is no vibration

Question 29

antinode

Answer 29

vibrations are at maximum amplitude

Question 30

can nodes and antinodes move?

Answer 30

no

Question 31

How do you calculate wavelength from nodes and atinodes?

Answer 31

The separation between adjacent nodes or antinodes = λ/2

Question 32

How do you determine if two points are in or out of phase from their nodes/antinodes?

Answer 32

Points between nodes are in phase with each other
Points that have an odd number of nodes between them are out of phase
Points that have an even number of nodes between them are in phase

Question 33

Experiment to investigate the superposition of sound

Answer 33

1) Use two speakers, a moderate distance apart, connected to the same signal generator to transmit sound waves
2) Walk along a line perpendicular to the speakers - you should hear alternating loud and quiet sounds
3) This is because in some places the wave from each speaker interfere constructively or destructively

Question 34

What is Young’s double slit experiment

Answer 34

A single source of light directed towards a double slit, which creates two coherent beams of light, creates an interference pattern

Question 35

True or False
Increasing the slit width increases the distance between two maxima

Answer 35

True

Question 36

Harmonics

Answer 36

Points where the stationary wave form doesn’t change because the waves in each direction are reinforcing each other