Chapter 11 - Waves 1

Question 1

What is a wave?

Answer 1

A physical phenomenon that transfers energy through a medium without transferring matter.

Question 2

What are the two types of waves? (Direction)

Answer 2

Transverse (direction energy transfer perpendicular to direction of oscillation)
Longitudinal (direction of energy transfer parallel to direction of oscillation)

Question 3

Wave equation

Answer 3

C = f x λ
Wave speed = frequency x wavelength

Question 4

Phase of a particle/point

Answer 4

Fraction of a complete cycle/wave that a particle/point is at (at any given moment)

Question 5

Phase difference

Answer 5

Difference in phase between two points along the same wave or between two waves at any given moment

Question 6

Wave lengths in radians

Answer 6

1 complete wave = 2π
1/2 a wave = 1π

Question 7

Phase formula and phase difference formula

Answer 7

Phase: (fraction of wave completed) x (2π)
Phase difference: (distance as fraction of wave) x (2π)
Phase difference = (phase in wave 1) - (phase in wave 2)

Question 8

what is reflection

Answer 8

when a wave reverses direction upon meeting the boundary between two different media.
Angle of incidence = angle of reflection (i = r)

Question 9

what is refraction

Answer 9

when a wave changes direction upon crossing the boundary between two different media

Question 10

Wave properties in a medium (3 properties)

Answer 10

Speed through a medium is constant
Therefore the higher the frequency, the shorter the wavelength

Question 11

Wave properties when passing through two media (3 properties)

Answer 11

Speed is fundamental property that changes when crossing between media
This leads to change in wavelength
Frequency remains constant

Question 12

refraction rules

Answer 12

sound waves speed up going into physically denser mediums
EM waves slow down going into optically denser mediums

Question 13

what is diffraction

Answer 13

phenomenon of waves spreading out when passing through a gap, or around an obstacle

Question 14

diffraction rules

Answer 14

the smaller the gap relative to wavelength of wave, the greater the diffraction
gap size has to be similar/same order of magnitude as wavelength for significant diffraction to occur
wave speed and wavelength don’t change upon diffraction

Question 15

what is polarisation

Answer 15

property of transverse waves which defines the plane of oscillation of the wave

Question 16

EM wave polarisation

Answer 16

Plane of polarisation of an EM wave is defined as the plane in which the electric field vibrates.

Question 17

what happens when a wave passes through a polarising filter?

Answer 17

the light passing through becomes polarised in one particular plane.
the intensity drops to half

Question 18

what happens when polarised wave passes through another polarising filter

Answer 18

if polarised wave matches the plane of alignment, 100% of wave is transmitted
if polarised wave meets plane of alignment at some angle, less than 100% of the wave is transmitted
if polarised wave meets the plane of alignment at 90 degrees, 0% of the wave is transmitted

Question 19

polarising light with reflection

Answer 19

light reflected off surfaces like metal and water is mostly polarised in the horizontal plane
sunglasses have vertically aligned polaroid filters to block all horizontally plane polarised light from reaching the eye (reducing glare)

Question 20

intensity formulae

Answer 20

I = P/A

I = P/(4πr^2)

Question 21

intensity relation to amplitude

Answer 21

intensity is proportional to amplitude squared

Question 22

Τhe Electromagnetic Spectrum

Answer 22

Radio, Micro, Infrared, Visible, Ultraviolet, X-rays, Gamma

Radio waves = lowest frequency, longest λ, least energetic
Gamma waves = highest frequency, shortest λ, most energetic

All EM waves have same speed in vacuum. In other media, the speed varies.

Question 23

refractive index formula

Answer 23

n = c/v

n is refractive index of a particular medium
c is speed of light in a vacuum
v is speed of light in that medium

Question 24

refractive index relation with angles of incidence and refraction

(when light is incident in a vacuum and refracts into a medium of refractive index)

Answer 24

n = sin i / sin r

Question 25

refractive index relation with angles of incidence and refraction

(when light is incident in a medium of refractive index and refracts into a vacuum)

Answer 25

1/n = sin i / sin r

Question 26

when light goes from one medium to another medium
(neither of which is a vacuum)

Answer 26

n1sin(θ1) = n2sin(θ2)

Question 27

total internal reflection, definition and conditions

Answer 27

phenomenon by which light completely reflects back at a boundary between two media, as opposed to transmitting across the boundary and refracting

1. medium within which light is incident has a larger refractive index than second medium.
2. angle of incidence exceeds the critical angle, for given medium

at the critical angle, the angle of refraction is 90 degrees… ray travels along boundary.

Question 28

result of angle of incidence (relative to critical angle)

Answer 28

θ < C: refraction and partial reflection occurs
θ = C: light refracts along the boundary between two media
θ > C: total internal reflection

Question 29

critical angle formula

Answer 29

sin(θc) = n2/n1

n2 = refractive index of second medium
n1 = refractive index of first medium
θc = critical angle

when at boundary between air/ vacuum:

sin(θc) = 1/n