Waves and Radiation Flashcards
waves transfer ____
energy from one place to another
types of wave
longitudinal and transverse
transverse wave
particles move perpendicular to the direction of travel of the wave
(remember slinky)
can travel through a medium or a vacuum
example of transverse wave
basically anything (EM spectrum)
longitudinal wave
particles move parallel to the direction of travel (remember slinky)
cannot travel through a vacuum
example of longitudinal wave
sound wave
trough
the lowest point of the wave
crest
the highest point of the wave
equilibrium position
the rest position of the wave
amplitude
the vertical distance from the equilibrium position to either the crest or the trough. measured in metres ( loudness)
wavelength
the horizontal distance between the same point in consecutive waves. measured in metres
period
time taken for one complete wave to pass a particular point
wave speed
distance the wave travels each second
frequency
number of waves per second that passes a particular point (pitch)
relationship for calculating frequency
f= N/t
relationship for calculating speed of wave w wavelength and frequency
v = f x wavelength
relationship for calculating period
T = 1/f
relationship for calculating wavelength
wavelength= d/N
relationship for calculating wave speed
v= d/t
diffraction
the effect of waves bending when they meet obstacles
diffraction effect____ as wavelength ___ or as gap width ___
increases, increases, decreases
shorter wavelengths do/ do not diffract as much as longer ones
do not
sound waves _____ travel through a vacuum
cannot
sound waves are created by
vibrations
oscilloscope
a machine that analyses sound waves. amplitude and frequency are examined
on an oscilloscope, changing the frequency or pitch means that
more or less waves will be displayed
on an oscilloscope, changing the amplitude or loudness of the signal
changes the vertical height of the trace on the screen
speed of light in air
3.0 x10 to the power of -8 ms-1
speed of sound in air
340 ms-1
what is faster, sound or light
light
measuring speed of sound experiments-
1- pistol and stopwatch (v =d/t)
2- pistol and stopwatch w wall (v=half d/t)
3- hammer, electronic timer, metal plate, microphones (start and stop)
range of human hearing
20-20,000 Hz
ultrasounds
high frequency vibrations beyond human hearing
uses for ultrasound
cleaning instruments
scanning unborn children in the womb
measuring blood flow through the heart
detecting kidney stones
sonar
detecting the depth of water
the device emits a series of ultrasound pulses and these are reflected by the sea bed and travel back towards the boat and are received by the sonar device. (2d=vt)
speed of sound in water
1500ms-1
musical instruments produce sound by
causing vibrations to pass through the air- membrane, string, air or reed
sound produced by a loudspeaker or headphones is produced by
a small current passing through a coil wire which becomes and electromagnet. this interacts w a permanent magnet to produce a movement of the cone which matches the fluctuations in the current.
loudness of a sound is measured in
decibels (dB)
sound levels above _____ can be dangerous
85dB
ACN
active noise cancellation- a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first
all waves in the EM spectrum are
transverse
all waves in the EM spectrum travel at
3.0 x10 to the power of 8ms-1
the higher the frequency of the wave=
the more energy they carry
order of EM spectrum from long wavelength to short wavelength/ low frequency to high frequency
radio waves microwaves infrared visible light ultraviolet rays X rays gamma rays
the energy transferred by these waves is related to their
frequency
wavefronts=
crests
distance between consecutive wavefronts =
wavelength
ray=
indicates direction of energy transfer, drawn perpendicular to the wavefront and has an arrow
reflection
when a wave encounters a boundary between 2 different mediums it experiences reflection
incident ray
ray approaching the boundary between 2 mediums
reflected ray
ray reflected away from the boundary between 2 mediums
angle of incidence
angle between normal and incident ray
angle of reflection
angle between normal and reflected ray
normal
dotted line drawn perpendicular to the boundary between 2 different mediums
refraction
a change in speed and wavelength . frequency stays the same. change in speed affects a change in direction