11 - Waves 1

Question 1

progressive wave

Answer 1

a wave in which the peaks and troughs, or compressions and rarefactions, move through the medium as energy in transferred

Question 2

longitudinal wave

Answer 2

a wave in which oscillations of the medium particles are parallel to the direction of wave travel and energy transfer

Question 3

transverse wave

Answer 3

a wave in which the oscillations of medium particles are perpendicular to the direction of wave travel and energy transfer

Question 4

p-waves

Answer 4

primary waves - longitudinal waves that travel through the Earth from an earthquake

Question 5

s-waves

Answer 5

secondary waves - transverse waves that travel through the Earth from an earthquake

Question 6

equilibrium position

Answer 6

the resting position of waves or particles in an oscillation

Question 7

restoring force

Answer 7

a force that tries to return a system to its equilibrium position

Question 8

peaks

Answer 8

the maximum positive amplitude of a transverse wave

Question 9

troughs

Answer 9

the maximum negative amplitude of a transverse wave

Question 10

compressions

Answer 10

a moving region in which the medium is denser or has a higher pressure than the surrounding medium

Question 11

rarefactions

Answer 11

a moving region in which the medium is less dense or has less pressure than the surrounding medium

Question 12

displacement (of a wave)

Answer 12

distance from the equilibrium position in a particular direction - a vector so can have either positive or negative value

Question 13

amplitude

Answer 13

maximum displacement from the equilibrium position (can be positive or negative)

Question 14

wavelength (λ)

Answer 14

minimum distance between two points in phase on adjacent waves - eg the distance from one peak to the next

Question 15

time period of oscillation (T)

Answer 15

the time taken for one oscillation, or time taken for a wave to move one whole wavelength past a given point

Question 16

frequency

Answer 16

number of wavelengths passing a given point per unit time

Question 17

wave speed

Answer 17

distance travelled by a wave per unit time

Question 18

the wave equation

Answer 18

v = f λ
wave speed = frequency x wavelength

Question 19

phase difference (Φ)

Answer 19

the difference in displacement between two oscillating objects, or the displacement of an oscillating object at different times

Question 20

in phase

Answer 20

particles oscillating perfectly in time with each other (reach maximum displacement at the same time) are in phase

Question 21

antiphase

Answer 21

particles oscillating completely out of step with each other (one reaches maximum positive displacement as the other reaches maximum negative displacement) are in antiphase

Question 22

phase difference formula

Answer 22

in radians: Φ = (x/λ)2π
in degrees: Φ = (x/λ)360
x is the distance between points

Question 23

wave profile

Answer 23

a graph showing the displacement of the particles in the wave against the distance along the wave

Question 24

reflection

Answer 24

change in direction of a wave at a boundary between different media so that the wave remains in the original medium

Question 25

law of reflection

Answer 25

the angle of incidence is equal to the angle of reflection

Question 26

angle of incidence

Answer 26

angle between the direction of travel of an incident wave and the normal at a boundary between two media

Question 27

angle of refraction

Answer 27

angle between the direction of travel of a reflected wave and the normal at a boundary between two media

Question 28

refraction

Answer 28

the change in direction of a wave as it changes speed when it passes from one medium to another

Question 29

diffraction

Answer 29

phenomenon in which waves passing through a gap or around an obstacle spread out

Question 30

polarisation

Answer 30

phenomenon in which oscillations of a transverse wave are limited to only one plane

Question 31

plane polarised

Answer 31

description of a transverse wave in which the oscillations are limited to only one plane

Question 32

partially polarised

Answer 32

description of a transverse wave in which there are more oscillations in one particular plane, but the wave is not completely plane polarised - occurs when transverse waves reflect off a surface

Question 33

unpolarised

Answer 33

description of a transverse wave in which the oscillations occur in many planes

Question 34

intensity

Answer 34

the radiant power passing through a surface per unit area

Question 35

electromagnetic (EM) waves

Answer 35

transverse waves with oscillating electric and magnetic components that do not need a medium to propagate

Question 36

electromagnetic spectrum

Answer 36

full range of frequencies of em waves from gamma rays to radio waves

Question 37

wavelength of radio waves

Answer 37

>10^6 - 10^-1 m

Question 38

wavelength of microwaves

Answer 38

10^-1 - 10^-3 m

Question 39

wavelength of infrared

Answer 39

10^-3 - 7x10^-7 m

Question 40

wavelength of visible light

Answer 40

7x10^-7 - 4x10^-7 m

Question 41

wavelength of ultraviolet

Answer 41

4x10^-7 - 10^-8 m

Question 42

wavelength of x-rays

Answer 42

10^-8 - 10^-13 m

Question 43

wavelength of gamma rays

Answer 43

10^-10 - <10^-16 m

Question 44

refractive index

Answer 44

speed of light in a vacuum / speed of light through the material

Question 45

total internal reflection (TIR)

Answer 45

the reflection of all light hitting a boundary between two media back into the original medium when the light is travelling through the medium with the higher refractive index and the incidence angle at the boundary is greater than the critical angle

Question 46

critical angle

Answer 46

the angle of incidence at the boundary between two media that will produce an angle of refraction of 90 degrees