Waves

Question 1

Wavelength - Radio waves

Answer 1

10^6 - 10^-1

Question 2

Wavelength - Microwaves

Answer 2

10^-1 - 10^-3

Question 3

Wavelength - Infrared

Answer 3

10^-3 - 7x10^-7

Question 4

Wavelength - visible

Answer 4

7x10^-7 - 4x10^-7

Question 5

Wavelength - ultraviolet

Answer 5

4x10^-7 - 10^-8

Question 6

Wavelength - X rays

Answer 6

10^-8 - 10^-13

Question 7

Wavelength - gamma rays

Answer 7

10^-10 - 10^-16

Question 8

Mechanical waves

Answer 8

regular vibration of particles

Question 9

Electromagnetic waves

Answer 9

oscillating electric and magnetic fields - they do not need particles so can pass through vacuum

Question 10

Longitudinal waves

Answer 10

displacement of particles is parallel to the direction of propagation of the wave’s energy

Question 11

Transverse waves

Answer 11

displacement of particles is perpendicular to the direction of propagation of the wave’s energy

Question 12

Progressive waves

Answer 12

transfer energy from one place to another

Question 13

Wavelength

Answer 13

distance from any point on the wave to the consecutive point that are in phase

Question 14

Displacement

Answer 14

distance of the point on the wave from its equilibrium position

Question 15

Amplitude

Answer 15

maximum displacement of a point on the wave from its equilibrium position

Question 16

Wave

Answer 16

a series of regular oscillations which transfer energy through matter or space

Question 17

Intensity of a wave

Answer 17

Rate of energy transmitted per unit area normal to wave velocity

Question 18

How does intensity of a wave decrease as it travels through space?

Answer 18

The waves spread out, some of the wave may be scattered or absorbed

Question 19

Phase difference

Answer 19

the fraction of one whole cycle between the vibrations

Question 20

Doppler effect

Answer 20

the apparent change in frequency (or wavelength) of a wave when the source is moving relative to the observer

Question 21

principle of superposition of waves

Answer 21

When two waves of the same type meet, they combine together. The total displacement of the resulting wave is the vector sum of the displacements of the individual waves at that point in space.

Question 22

Nodes

Answer 22

the points on the wave that do not move

Question 23

Antinodes

Answer 23

the points on the wave that oscillates with maximum amplitude

Question 24

Explain the formation of antinodes

Answer 24

when two waves arrive at the same point IN PHASE. The two waves superimpose CONSTRUCTIVELY so their two displacements add together to give maximum displacement (constructive interference)

Question 25

Explain the formation of nodes

Answer 25

when two waves arrive at the same point IN ANTIPHASE. The two waves superimpose DESTRUCTIVELY so their two displacements add together to give ZERO displacement (destructive interference)

Question 26

wave speed of progressive wave

Answer 26

speed at which energy is transferred

Question 27

period

Answer 27

time taken for one complete oscillation to pass a point

Question 28

frequency

Answer 28

number of oscillation per unit time of the source

Question 29

wave speed of a stationary wave

Answer 29

rate of transfer of energy of the wave fronts of the two progressive waves that superpose to create the stationary wave.

Question 30

condition for stationary wave to form

Answer 30

- two progressive waves of the same frequency, same type and similar amplitude - travelling in opposite directions - overlap so that superposition takes place

Question 31

how to use CRO

Answer 31

- adjust the time base to get approx. 2 waves on screen - count the number of divisions for one complete wave - multiply the number of division by time base setting to get the time - use equation F=1/T to find the frequency

Question 32

differences between progressive and stationary waves

Answer 32

- progressive waves do not have nodes or antinodes, stationary waves do - on progressive waves, two consecutive points are not in phase, on stationary waves, they are in phase

Question 33

similarities between progressive and stationary waves

Answer 33

air particles vibrate parallel to the direction of wave travel

Question 34

Suggest how stationary electromagnetic waves might be set up

Answer 34

A microwave transmitter is placed a distance from a metal plate that reflects the emitted waves. When the position of the transmitter is adjusted to achieve a suitable resonant length between transmitter and reflector, stationary waves would be formed by the superposition of the emitted and reflected waves.

Question 35

path difference between two constructive waves

Answer 35

nλ

Question 36

path difference between two destructive waves

Answer 36

(n+1/2) λ

Question 37

what is meant by the term 'coherence'

Answer 37

- two waves of same type - constant phase difference - overlap

Question 38

How coherent source is produced?

Answer 38

same source diffracted by double slit

Question 39

What is observed on screen by double slit?

Answer 39

- bright and dark fringes

Question 40

How to diffract a white light source?

Answer 40

use a coloured filter then pass through single slit, then double slit

Question 41

How can fringes be seen more clearly?

Answer 41

- screen is moved further away - room is dark - slits are very close together

Question 42

monochromatic

Answer 42

light of a single wavelength / frequency

Question 43

How the wavelength can be found using young's double slit (equation)

Answer 43

λ = ax/D

Question 44

How to measure λ accurately in Young's double slit?

Answer 44

large D to give greater fringe spacing. Measure across several fringes, repeat for different distances. Could plot a graph of X v D and find gradient.

Question 45

What is a diffraction grating?

Answer 45

A large number of equally spaced lines ruled on a glass or plastic slide

Question 46

What precautions you should take when calculating a value for wavelength using laser?

Answer 46

- protective goggles - not looking directly into laser - avoid reflections (shiny surfaces, jewellery)

Question 47

Explain the term interference (same for principle of superposition)

Answer 47

when two waves meet, the resultant displacement is the sum of individual displacement

Question 48

Dispersion

Answer 48

The splitting of wave into different wavelengths