p12 Flashcards
what is a transverse wave?
waves where the points along its lengths vibrate at 90 degrees to the direction of energy transfer
eg: ripples on the surface of water, electromagnetic waves
what is a longitudinal wave?
waves where the points along its length vibrate parallel to the direction of energy transfer.
eg: sound waves, pressure waves caused by repeated movements in a liquid or a gas
differences between longitudinal and transverse waves
transverse waves have
- peaks and troughs,
- their vibrations are 90 degrees to the direction of energy transfer,
- only electromagnetic waves can travel in vaccum,
- they can move in liquids and solids, but not gases,
- constant density and pressure
what is the amplitude of the wave?
maximum displacement of a point on a wave from its undisturbed position
what is the wavelength of a wave
the distance from a point on one wave to the equivalent point on the adjecant wave
what is frequency of wave?
the number of waves passing a point each second
what is range of human hearing and why can they not hear outside this range?
20Hz to 20kHz.
The conversion of sound waves to vibrations of solids works over a limited frequency range.
This restricts the limits of human hearing
how do u hear sound?
Within the ear, sound waves cause the ear drum and other parts to vibrate which causes the sensation of sound.
what is the purpose of the ripple tank in the experiment?
to create small waves in water
what is the purpose of the light source in the experiment?
to illuminate the waves to create shadows
what is the purpose of the white sheet of paper in the experiment ?
to provide a white backgound yo act as a screen for the wavefront shadows
ripple tank experiment steps
- Set up the apparatus as shown and fill the ripple tank with water to a depth of no more than 1 cm
- Turn on the power supply and the light source to produce a wave pattern on the screen
- The wavelength of the waves can be determined by using a ruler to measure the length of the screen and dividing this distance by the number of wavefronts
- The frequency can be determined by timing how long it takes for a given number of waves to pass a particular point and dividing the number of wavefronts by the time taken
- Record the frequency and wavelength in a table and repeat the measurements
define reflection
when a wave hits a boundary between two media and does not pass through, but instead stays in the original medium
define transmission
when a wave passes through a substance
define absorption
energy is transferred from the wave into the particles of a substance
what are some uses of sound waves?
echo sounding - used by ships to detect the ocean floor
ultrasound - looking inside human body
seismic activity - to investigate the structure of the earth
what is ultrasound?
sound waves with a frequency above the human hearing range
how is ultrasound used for detection?
they are partially reflected when they meed a boundary between two different media.
the time taken for the reflections to reach a detector can be used to determine how far away sich a boundary is
echo sounding
uses ultrasound to detect objects underwater
- the sound is reflected off the ocean bottom.
- the time it takes for the soundwave to retur is used to calculate the depth of the water
ultrasound in medicine
used to
- construct an image of foetus in womb
- to generate images of organs and internal structures
- as medical treatment such as removing kidney stones
what are P waves
they are longitudinal seismic waves
they travel at different speeds through liquids and solids
what are S waves
transverse seismic waves and cannot travel through a liquid
