Waves Flashcards
(54 cards)
Define transverse waves
oscillations are perpendicuar to direction of energy transfer
Define longitudinal waves
oscillations are parallel to direction of energy transfer
define amplitude
maximum displacement of a point on a wavenfrom its undisturbed position
define frequency
number of waves passing a fixed point per second
define time period
time taken for one complete wave to pass a fixed point
1/frequency= time period and
define wavelength
distance from one point on a wave to the equivalent point on the next wave
define wave speed
distanced travelled by each wave per second, and the speed at which energy is transferred by the wave
what are the compressed and decompressed areas called on longitudinal waves
compressed-compression
decompressed-rarefaction
what are the highest and lowest point on transverse waves called
highest-peaks
lowest-troughs
Describe a method to measure the speed of sound waves in air
-2 people stood 500 metres apart
-person A holds cymbals
-person B holds a timer
-B starts timer when they see A clash cymbals together
-then stop timer when hear sound of them clashing
-can calculate speed of sound waves by dividing the distance travelled by time taken
RPA METHOD:
Ripple Tank
ripple tank:
-shallow tray of water with vibrating bar in water
-bar connected to a power pack
-when bar vibrates, creates waves across surface of water
-above tank:lamp, below tank:white sheet of paper
(when light shines through the water, it produces an image of the waves on the paper)
method after setup:
1.
-record waves using a mobile phone, have timer in view (to be able to play back recording at different speeds / freeze it)
-align ruler with waves (in frame too)
-measure distance between 1 wave and 10 waves further
-divide by ten to get wavelength
-count number of waves passing point in 10 seconds
-divide by ten to give frequency
-use formula to calculate wave speed
2.
-select a wave and measure time it takes to move length of the tank
-calculate speed using formula
RPA METHOD:
waves in a solid
set up:
-string with one end attached to a vibration generator
-hanging mass at other end of string to keep it taut
-v generator is attached to a signal generator (allows us to change the frequency of vibration of the string)
-when power is turned on, string vibrates
-use wooden bridge to adjust wavelength
method:
-standing wave due to resonance
-measure total length using ruler from wooden bridge to vibration generator
-read frequency from signal generator
-calculate wave speed using formula
increase frequency
(wave speed does not depend on frequency or wavelength-depends on taughtness of string and mass per cm)
-n
RPA METHOD:
Reflection & Refraction
use: raybox, lens, slit (to produce narrow wavelength of light
(rayboxed get hot so must be switched off when not being used)
-take A3 paper and draw a straight line down centre using ruler
-use protractor to draw line at right angles (normal)
-place glass block against 1st line
-draw around glass block
-(turn off all lights in room)
-use ray box to direct ray of light so it hits box at normal
-mark reflected ray, incident and transmitted ray with crosses (transmitted ray with 2 crosses)
-turn on lights and turn off raybox
-remove glass block
-draw rays
-draw path of ray through box
-use protractor to measure angle of incidence and angle of reflection against the normal
-angle of refraction too (between normal and path of ray through box)
-repeat with other materials of block (e.g perspex)
-angle of reflection will be the sane, angle of refraction will change
what are the 2 main properties of a sound wave
mechanical waves
(need a solid/liquid/gas medium to travel through and can’t travel without a medium)
longitudinal waves
(oscillations are parallel to direction of energy transfer)
what happens when sound waves go from air to solid
they cause vibrations of same frequency in the solid
how can we hear?
sound waves cause solid parts of the ear (e.g eardrum) to vibrate
brain converts vibrations into what we hear
however, we can only hear a limited frequency
(20Hz to 20,000 Hz)
whatre the relationships between frequency, pitch, amplitude, and volume
higher frequency=higher pitch
higher amplitude=louder sound
what happens to the speed of waves when they move from 1 medium to another
(example?)
their speed can change (e.g sound waves travel faster in solids)
how can we view the features of sound waves
+what is 1 problem with this method
by connecting a microphone to a cathode ray oscilloscope
problem: represents sound waves as if they were transverse rays
why can’t sound pass through a vacuum
as there are no particles
what’s it called when sound waves are reflected
an echo
What is meant by an ultrasound
sound waves with a frequency higher than the upper range of the limit of human hearing
what is 1 key property of ultrasound waves
-ultrasound waves are always partially reflected when they meet a boundary
How can ultrasounds be used in imaging
as ultrasounds always partially reflect off a boundary
distance to boundary can be found by timing how long it takes for a ultrasound reflection to come back to a detector
