Waves Flashcards
are typically disturbances in some medium
waves
electromagnetic waves include
light or radio waves
movement of gas molecules
sound waves
movement in solids
seismic waves
occurs whenever a system is disturbed from equilibrium due to transfer of energy and when the disturbance can travel or propagate from one region of the system to another.
waves
aves can show a visible disturbance or oscillation in the medium in which they occur; however, waves do not move ____, they only transfer ____.
matter
energy
a vibration or a disturbance in space.
wave
a wave can be:
mechanical wave
electromagnetic wave
wave that requires a medium
mechanical waves
wave that does not require a medium
electromagnetic waves
two types of mechnical waves
transverse wave
longitudinal wave
cause the medium to move perpendicular to the direction of the wave.
transverse wave
waves cause the medium to move parallel to the direction of the wave.
longitudinal
example of electromagnetic waves
light
microwave
infrared
x-rays
UV rays
radiowaves
requires a medium to transfer energy from one location to another.
mechanical wave
example of mechanical wave
sound waves
ocean waves
ripples in water
earthquake
is the substance through which a wave can travel
medium
example of medium
air
water
strings
solids
liquids
gases
As the wave moves through the medium, its ____will oscillate back and forth, but do not actually move with the wave.
particles
types of mechanical waves
transverse wave
longitudinal wave
energy moves up and down or side to side while traveling forward
transverse wave
study the parts of transverse wave
+
energy moves along the medium while traveling forward.
longitudinal wave
parts of a longiudinal wave
+1
particles are closed together.
compression
- particles are spread apart.
rarefaction
- it does not require any material medium for its propagation and can travel even through a vacuum; caused by varying electric and magnetic fields.
electromagnetic waves
wave behavior (4)
reflection
refraction
diffraction
interference
wavelength from longest to shortest
radio (10^3)
microwave (10^-2)
infrared (10^-5)
visible (0.5x10^-6)
ultraviolet (10^-8)
x-ray (10^-10)
gamma ray (10^-12)
wavelength of radio waves
10^3
wavelength of microwave
10^-2
wavelength of infrared
(10^-5)
wavelength of visible light
0.5x10^-6
wavelength of ultraviolet light
10^-8
wavelength of xray
10^-10
wavelength of gamma ray
10^-12
_____ wavelength, ____ frequency
decreasing
increasing
the distance between one point on a wave and the exact same place on the next wave
wavelength
It is the wave motion in one period and is often measured from crest to crest along a wave or from trough to trough along a wave
wavelength
indicates how many waves go past a point in one second; unit of measurement is hertz (Hz).
frequency
frequency’s unit of measurement is ____
hertz (Hz)
the higher the _____, the more energy in the wave
frequency
is the reciprocal of of frequency, measured in seconds.
period (T)
period is measured in
seconds
relationship of frequency and period
T = 1/f
maximum displacement of vibrating particles of the medium from their equilibrium positions.
amplitude
distance travelled by a wave crest in one period
wave velocity
It depends on the medium in which the wave is traveling. It varies in solids, liquids and gases.
wave velocity
wave velocity formula
v = λf or v = λ/T
where v - wave veloicty
λ - wavelength
F - frequency
T - period
λ stands for
wavelength
F stands for
frequency
T stands for
period
An observer sitting on a shore counts the waves and finds that there are 6 waves per minute hitting the shore. She measures the distance between consecutive crests to be 10 m. What is the velocity of the waves?
f = 6 waves/min * 1 min/60s = 0.10 wave/s
v =λf = 10 m x 0.10/s = 1.0 m/s
Medical ultrasound waves travel at about 1500 m/s in soft tissue. Higher frequencies provide clearer images but don’t penetrate to deeper organs.
Find the wavelengths of (a) 8.0 -MHz ultrasound used in fetal imaging and (b) 3.5 -MHz ultrasound used to image adult’s kidneys. Express your
answers in mm.
a = λ = v/f = 1500 m/s / 8.0x10^6 /s = 1.88 x10^-4 m x 1000/1 = 0.188m
b= λ = v/f = 1500 m/s / 3.5x10^6/s = 4.29 x10^-4 m x 1000 mm/1m = 0.429 mm
If a wave is to travel through a medium such as water, air, steel or a stretched string, it must cause the particles of that medium to oscillate as it passes, which requires both ___(for kinetic energy) and ____( for potential energy)
mass
elasticity
the velocity of the wave in a string/cord is determined by
√ elastic property/ inertial property
elastic property is
tension (F)
inertial property is
mass density/mass per unit length
the bouncing back of a wave as it meets a surface or boundary
reflection
can all types of wave be reflected?
yes
The angle of incidence (Ɵi) is equal to the angle of the reflected wave (Ɵr)”
law of reflection
an imaginary line that is perpendicular to the surface
normal
-how much of the wave that is reflected depends on the impedance between the two mediums.
normal and surface
describes the difference in densities of the two mediums, the greater the difference in mediums, the greater the
.
impedance
he greater the difference in mediums, the greater the
.
impedance
-As the impedance increases, more of the wave’s energy is ___instead of being transmitted into the next medium.
reflected
occurs when a wave bends as it moves from one substance into another.
refraction
___ waves may change speed and wavelength but do not change frequency
refracted
refracted waves may change ___ and ___ but do not change frequency
speed
wavelength
the bending of a wave around the edges of an opening or an obstacle.
diffraction
a wide gap will have a __ diffraction effect
small
a narrow gap will have a ___ diffraction effect
large
a large wavelength will have a ___ diffraction
large
- the phenomenon that occurs when two waves meet while traveling at the same medium; two or more waves combine to form a new wave
interference
occurs when the wave amplitudes reinforce each other, building a wave of even greater amplitude
constructive interference
occurs when the wave amplitudes oppose each other resulting in waves of reduced amplitude
destructive inference
“When 2 waves meet while traveling through a medium at the same time, the result is a wave whose displacement is equal to
the vector sum of the displacement of the two waves”
are the result of the interference of two identical waves with the same frequency a nd the same amplitude traveling in opposite direction.
standing waves
point on standing wave that always undergo complete destructive interference and with zero amplitude
node
point halfway between two nodes at which maximum amplitude occurs
antinode
has the lowest frequency and longest wavelength
first harmonic standing wave
It consists of a node at both ends and one antinode between them
fundamental frequency (first harmonic) standing wave
L in a standing wave refers to the
1/2 of wavelength λ
thus λ = ___ L
2
frequency when L is given
v / 2L
fn formula
fn = n/2 v/L
All mechanical waves are capable of transporting ____ when they propagate through a medium
energy
the energy is carried out by ___ motion of the molecules that composes the medium
vibrational motion
the energy transported by wave is prportional to the square of the ____and to the square of the ___
frequency
amplitude
formula for power
p = x^2 (Where x is amplitude)
on a calm day, the waves reaching a beach have an amplitude of 0.1 m. On a much windier day, the amplitude is 0.5m, although the speed and wavelength of the waves is the same. What is the ratio of the power delivered by the waves on the windy day compared to that on a calm day?
25
velocity formula based on elasticity and inertial property
v = √F /µ
a flexible cable, 30m long and weighing 70 N, is stretched between two poles by a force of 2.0 kN, if the cable is struck sideways at one end, how long will it take the transverse wave to travel to the other end and return?
v = 91.67 m/s
tT = 0.65s
the time required for a wave to complete one full cycle is called the wave’s ___
period
if the amplitude of a wave traveliongin a rope is doubled, the speed of the wave of the rope will decrease
false
