oscilltions and waves Flashcards
time period
the amount of time it takes an oscillating particle to complete one cycle (an oscillation)
displacement
the distance of the oscillating object from equilibrium
wave
propagation of energy through a material substance
refraction
the bending of waves through materials due to a difference in speed
amplitude
the maximum displacement from equilibrium an oscillating particle reaches
transverse wave
a wave in which the direction of disturbance is perpendicular to the direction of energy transfer
longitudinal wave
a wave in which the disturbance is parallel to the direction of energy transfer
what is light
an electromagnetic transverse wave
reflection
when a wave hits the boundary between two media part of the wave comes back at the same angle
what type of wave is sound
longitudinal
velocity of a sound wave travelling through air at 20*C and normal atmospheric pressure
340m/s
what happens to the speed of sound at higher temperatures?
velocity is greater since the molecules move faster
ray
shows the direction of a wave
wavefront
line joining points between waves
relationship between rays and wavefronts
ray is perpendicular to wavefront
if wavelength is shorter, velocity is
decreased
how can u tell from a graph that smth’s oscillating?
sign of velocity changes -> direction changes -> body is oscillating
what does the area under a velocity time graph show?
the displacement
explain why you can only refer to the speed of light rather than velocity
velocity = displacement/time where displacement is the distance moved in a certain direction, however light spreads out in all directions
state the principle of superposition
superposition is what happens when two waves coincide: the displacements of waves add vectorially to produce a resultant wave
refraction
when a wave hits the boundary between two media part of the wave passes into the new medium with a change of angle
diffraction
when a wave passes through a narrow opening it spreads out
superposition
when two waves coincide the displacements at a point add
wave speed
the distance travelled by the wave profile per unit time
nodes
positions where the displacement is always 0, separated by (wavelength/2)
antinodes
positions of maximum displacement
state the principle of superposition
superposition is what happens when two waves coincide: the displacements of waves add vectorially to produce a resultant wave
refraction
when a wave hits the boundary between two media part of the wave passes into the new medium with a change of angle
diffraction
when a wave passes through a narrow opening it spreads out
superposition
when two waves coincide the displacements at a point add
wave speed
the distance travelled by the wave profile per unit time
when are standing waves formed in strings?
formed when two waves of the same frequency travel in opposite directions along the same string. Happens when a wave reflects back and forth along a clamped string
constructive interference
if waves add when they superpose.
graph of displacement against time
sine
graph of velocity against time
cosine
graph of acceleration against time
sine graph
radian definition
arc length/radius
why do radians have no units
ratio of two lengths
what does narrowing the slit in youngs experiment do
pattern becomes more spread out
what are youngs fringes used to measure
the wavelength of light
in refraction what changes and what stays the same
wavelength changes but frequency stays the same
how and why will youngs fringes change if the filter is switched from red to blue
blue light has a shorter wavelength so the fringes will be closer together
in the equation s =wavelengthD/d, what are s, D and d?
s = distance between 2 successive fringes D = distance from slits to screen d = distance between slits
when is velocity of an oscillator maximum?
when the bob passes the equilibrium point
what is the intensity of light measured in
Wm^-2
what is intensity
energy per area
phase difference
the difference between two oscillations that are not in time with each other
measured in terms of angle in radians, a difference of pi is completely out of phase
a path difference of 1/2wavelength introduces a phase difference of
pi
distance between 2 nodes
half wavelength
gamma ray wavelength order of magnitude
10^-12
x ray wavelength order of magnitude
10^-10
what does it mean if numbers differ by one order of magnitude
x is about 10x different in quantity to y
ultraviolet wavelength order of magnitude
10^-8
visible light wavelength order of magnitude
0.5x10^-6
infrared wavelength order of magnitude
10^-5
microwave wavelength order of magnitude
10^-2
radio wavelength order of magnitude
10^3
Incident radiation from Sun calculate
calculated by multiplying the Solar Constant by the cross-sectional surface area of the Earth.
calculate Radiation reflected by the Earth
Multiply the radiation incident on the Earth by the albedo of the Earth
calculate Radiation emitted by the Earth
Found by using the Stefan-Boltzmann Law (must use the total surface area of the Earth as energy is emitted in all directions). Unless stated otherwise (such as in the example to the left) assume emissivity is 1.
order of magnitude surface area of earth in m
10^14
sa of earth in m
5.1x10^14
how do control rods slow down the reaction
absorbing neutrons, preventing them
from being absorbed by 235U, leading to
further fissions.
why does a pool look shallower than it actually is
light bends as it comes out of the pool (refraction)
why is the magnitude of the tension in the string of a pendulum at its midpoint of oscillation greater than the weight of the pendulum bob?
the pendulum bob accelerates towards the centre of the circular path, hence there is a force upwards that adds to the tension produced by the weight
what happens if angle of incidence is the critical angle
refracted ray is refracted along the boundary
what happens if angle of incidence is greater than critical angle
total internal reflection
phase difference between particles standing wave vs progressive wave
All points between two nodes on a standing wave are in phase whereas points on a progressive wave that are closer than one wavelength are all out of phase
the total energy of an object undergoing simple harmonic motion is proportional to…?
its mass
