Waves -Terms and definitions Flashcards
Energy Transfer
Wave motion, in general, is a process in which kinetic energy is transferred from one point to another without any transfer of matter between the points
Mechanical waves
requires a material medium
eg. sound waves
Electromagnetic waves
do not require a medium (can travel in vacuum)
eg. light
Longitudinal waves
vibrate parallel to the direction of motion
eg. sound waves
Transverse waves
vibrate perpendicular to the direction of motion
eg. light, water
Amplitude (A)
the maximum distance a particle is displaced from its rest position
Wavelength (λ)
The distance between two successive corresponding positions in a wave (m)
Wave velocity (v)
the velocity of the wave shape
Frequency (f)
Number of waves to pass a point in a second
Hertz (Hz)
Period (T)
The time (s) it takes for one wave to pass a point Seconds (s)
T=1/f
T = Period (s) f = frequency (Hz)
f=1/T
f = frequency (Hz) T = Period (s)
v=fλ
v = velocity (m/s) f = frequency (Hz) λ = wavelength (m)
Pulse in Heavy String
Travels slowly
Pulse in Light String
Travels quickly
Deepwater -> shallow water (refraction)
Waves slow down
wavelength increases
bends behind
shallow water -> deep water (refraction)
Wave speeds up
wavelength decreases
bends forwards
Refraction
change in speed when a wave travels from one medium into another
frequency (f) does not change
Speed (v) changes
wavelength (λ) changes
less optically dense medium -> more optically dense
slows down
bends towards the normal
Superposition
Ability for waves to superimpose (add their displacements and their energy) as they move through each other
Interference
pattern of waves produced by two source points
Principle of superposition
two waves to be ‘added’ together by adding their displacements together at each instant in time
Constructive interference
crest meets crest or
trough meets trough
Total Internal Reflection
Angle of incidence is greater than the critical angle, all the light reaching the boundary is reflected.
Criteria:
1. Must go from optically dense -> less dense
2. 0i must be greater than critical angle
Nodal lines
(flat)
destructive interference
amplitude = 0
wave arrive 180° out of phase
antinodal lines
(Large height)
constructive interference
maximum amplitude
wave arrive 180° in phase
Path Difference
PS1-PS2 = (n-(1/2)λ
PS1 =
PS2 =
n =
λ =
Path Difference
PS1-PS2 = nλ
PS1 =
PS2 =
n =
λ =
Speed of light
3.00x10^8 m/s
Laws of Reflection
Incident ray, reflected ray, normal line all lie in the same plane
the angle of incidence is equal to the angle of reflection
1/f = 1/di + 1/do
f = focal length di = distance of image do = distance of object
NOTE:
f is negative when convex mirror
di is negative when virtual image
m = hi/ho = di/do
m = magnification hi = image height ho = object height di = image distance do = object distance
NOTE:
f is negative when convex mirror
di is negative when virtual image
Critical Angle
angle of refraction is 90° to the angle of incidence
Refractive index
n = sin01/sin02 01 = incident angle 02 = refraction angle n = optic density/refractive index
Snell’s law
λ1/λ2 = v1/v2 = sin01/sin02 = n2/n1
n1sin01 = n2sin02
λ = wavelength (m) v = velocity (m/s) 01 = incident ray 02 = refractive ray n2 = refractive index of medium 1 n1 = refractive index of medium 1
Dispersion
different frequencies of light splitting up through a prism
red has longest λ so bends the least
violet has shortest λ so bends the most
Concave mirror within focal length
Virtual
Enlarged
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