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topic 5
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- 1—the force acting on this person could be fatal.
- 2change in momentumrapid changes in momentum lead huge forces applying and these are EXTREMELY DANGEROUS
- 3how to reduce the DANGERmaking the momentum happen over a longer time.
- 4how can we do thatall of these slows down the MOMENTUM CHANGE and so reduced the forces acting and the risks of injury
- 5which are the two categories of waves and state examplesthese are TRANSVERSE and LONGITUDINAL waves. ripples transfer kinetic energy, sound waves transfer sound energy
- 6what do ALL waves dothey transfer energy from one place to another
- 7explain transverse waves ex ripplesthe wave is moving up and down (oscillating). the direction of the oscillation is perpendicular to the energy transfer. the oscillations are up and down but the energy transfer is SIDEWAYS.
- 8explain by which regions the longitudinal waves are made up of ex sound travelling through airsound waves travels as particles in the air moves side to side.
we've got regions with COMPRESSIONS and we've got regions with RAREFACTIONS
- 9explain the longitudinal wavesthe oscillations are parallel to the direction of energy transfer
- 10the main difference between longitudinal and transverse wavesall longitudinal waves REQUIRE a medium to travel in like air, liquid and solid and not ALL transverse waves require that
- 11what travels in ripples and sound wavesit is the wave that travels and NOT the medium or the air.
- 12definition of amplitudemaximum displacement of a point on a wave, away from its undisturbed position
- 13definition of wavelength in a transverse wavedistance point on a wave to the equivalent point on the adjacent wave.
- 14how do we measure wavelength in a longitudinal wavewe measure from one compression/rarefaction to the next compression/ rarefaction
- 15explain frequencynumber of waves passing a point each second. this one is 5 Hz/ 5 waves per second.
- 16explain periodis the time for ONE wave to pass a point
- 17STATE THE EQUATION of frequency and period.
- 18what is the wave speed and state the equationspeed at which a wave moves through a medium
- 19describe a method to measure the speed of sound waves in airwe use two people separated by a distance of 500 metres. person a is holding a pair of cymbals and person b a timer.
person b starts the timer when she sees person a clash the cymbals together and then stops timing when she hears the sound of the cymbals clashing. we can calculate then the speed by dividing the distance by the time taken - 20what could be the problems with this experiment- every person has a different reaction time
- it takes fractions of second to between seeing and starting the timer
- it takes fractions of second between hearing and stopping the timer - 21how can we reduce the this error- having larger number of observers with timers discarding any anomalous result and then calculate the mean value
- we can reduce the hearing the sound and stopping by increasing the distance between them because longer distance longer time so its easier to stop and start the timer at correct times - 22explain the ripple tank practicala ripple tank is used to observe the features of the water waves, in the water there is vibrating bar connected to a power pack.
- when the bar vibrates it creates waves across the surface of the water
- above the ripple tank we have a lamp
- below the tank we have a sheet of white paper
- when light shines it produces an image on the sheet of paper
with this set up we then measure the frequency , wavelength and speed of the waves
- 23how to measure the wavelength on this experimentwe place a ruler on the paper and freeze the image and then measure the distance between one wave and 10 further.
so we find 10 wavelength and divide it by 10 to find one
- 24how to measure the frequency on this experimentwe need to place a timer next to the paper and count the number of waves passing a point in one second or in 10 second and then divide by 10.
- 25how to measure the speed on this experimentwe just use the wave equation or we can divide the distance travelled by the time taken to travel this distance
- 26explain the waves in a solid practical- a string is attached to a vibration generator
- at the other hand of the string we have have a hanging mass that keeps the string taut
- the vibration generator is attached to a signal generator that allows us to change the frequency of the string
- when we turn on the power the string vibrates
- at a certain frequency we get a standing wave due to an effect called resonance
- we measure the total length of this standing wave with a ruler.
now we can measure the speed of the wave because each wave is a half wave 2 times to make 1 wave. ex. 2.15 - 27how can you measure the wave speed in this experimentthis time just with the wave speed formula
- 28what happens if we now increase the frequencythe standing wave will change but in this case we have 3 half waves
- 29how can we calculate the wavelength thenwe divide the total length by the 3 halves and then times it by 2 to find the wavelength of a wave and we will find ex. 2.13
- 30what does the wavelength depend onthat the wave speed does not depend on the frequency or the wavelength
it depend on the toughness of the string and the mass per cm - 31what happens when a wave hits a boundary with a different material3 things could happen : reflection, absorption, transmission.
- 32explain transmissionpassing through the material has not changed the wave
- 33explain absorptionthe energy of the wave can be absorbed by the material
- 34explain reflectionwhen the wave may simply be reflected off the surface of the material
- 35how do we know which of these will happendepending on the wavelength and on the material
- 36draw the RAY diagram of an reflected object by a mirror
- 37how to find the reflection of an object with a RAY diagram
- 38practical to investigate the reflection of light in different surfaces and substanceswe use( to produce a narrow of light) :
- ray box( switch them off when not used)
- lens
- slit
- we take a piece of A3 paper and draw a straight line using a rule
- use a protractor to draw a line at right angles , this is the normal
- we place a glass box against the first line so that the normal is at the centre of this box
- draw around the glass box
- turn out the lights
- we use the ray box to direct a ray of light hitting at the normal( incident ray)
- we can see a ray reflects from the surface of the block and another one leaving from the opposite side (transmitted ray)
- we mark all the rays with crosses
- we turn on the room light and switch off the ray box
- we remove the glass block
- we draw the incident and reflected ray and transmitted ray
- we draw also a line to show the path of the transmitted ray through the glass block( refraction)
- we use a protractor to measure the important angles ( incidence, reflection and refraction )
- do this experiment with another block , not the glass one but for example a plastic one.
what we should find out is that the - 39state an example of sound wave travelling from air to a solida microphone
- 40explain how a microphone workswhen sound hits the paper cone this causes it to vibrate and the microphone converts it to electrical signals
- 41sound waves in a human ear and state the range of frequencysound waves hit the EARDRUM which is a thin membrane that will vibrate with other parts of the inner ear and this causes the sensation of sound.
from 20 Hz to 20 000 Hz - 42what does sound waves do when passing through a solidthey will TRIGGER the vibration but only at a certain frequency , if the frequency is not in the range of frequency to make the object vibrate it will not vibrate
- 43what does changes when sound travels through a mediumspeed changes when passing through different materials.
solid material = more speed then gasses - 44why the sound travels with more speed in solidsbecause the particles are held together so more vibration can occur.
- 45what changes when the speed changes and what does not changealso the wavelength changes but the frequency ALWAYS stays the same when passing through mediums
- 46why does the frequency NEVER changebecause you will need to create or destroy waves at a boundary which is IMPOSSIBLE
- 47how does frequency and amplitude EFFECT sound- a high frequency produces a high pitch, low frequency produces a low pitch
- a high amplitude produces a loud sound , a low amplitude produces a quiet sound - 48what do we use to view the features of sound wavesmicrophone connected to a cathode ray oscilloscope
- 49what is the problem with thisthat it represents the features of sound waves but as if they were TRANSVERSAL waves.
- 50what does this graph representsa high frequency produces a high pitch, low frequency produces a low pitch
- 51how can the sound waves ONLY movepassing through a medium because they only move by vibrating particles and cannot pass through a vacuum because there are not particles in it
- 52can sound waves be reflectedyes and the sound reflected wave is called echo.
- 53what is ULTRASOUNDis a SOUND WAVE that has a frequency HIGHER than the upper limit of human hearing and partially reflects at the boundary between two different densities.
20Hz to 20 000 HZ so ultrasound is at least 20 000 Hz - 54where is ultrasound used inmedicine, industries,
- 55what does ultrasound SCANNING in medicine do and why is it saferproduce images of internal organs: kidneys, foetus, heart, all organs not surrounded by bone. it is safer then x-rays because does not cause MUTATIONS and does not increase the risks of cancer
- 56what else we can use ultrasounds scanningto scan a pipe detecting hidden defects
- 57how can we determine distance with ULTRASOUND
- 58how to measure the distance by emitting ULTRASOUNDexample it takes 1.2 second for the reflection to return the ship calculate the depth otherwise called DISTANCE.
so we know the speed of ultrasound is 1600 m/s so we can easily find the distance by the formula : distance= speed x time
the distance that we will found is the distance travelled from the ship to the sea bed and back to the ship again.
so how can we find the distance/depth ? we have to divide our total distance by 2
- 59name the part of the earthsolid crust(solid), mantle (solid), inner core(solid), outer core (liquid)
- 60how does scientists know the inner of the earth is like thisbecause of earthquakes
- 61how does earthquakes workit Is caused by the sudden movement of TECTONIC PLATES in the earth's CRUST, this causes SEISMIC WAVES that carry ENERGY out of the earthquake, these SEISMIC WAVES pass through the earth detected by SEISMOMETERS. and so the PATTERN of these waves gives us informations about the inner structure of the earth
- 62what are the types of SEISMIC WAVESp waves and S waves
- 63describe p waveslongitudinal , can pass through solids and liquids, and travel faster than S waves.
they are not detected on the p- shadow zones because they travel faster in solids then in liquids, so in liquids they tend to slow down(outer core) and they REFRACT. - 64describe S wavestransverse , pass through solids, CURVED PATHS due to change in density of the earth , not detected in s- waves shadow zone bc s- waves cannot pass through liquids and that proves that the OUTER CORE is liquid.
- 65what does SEISMOMETERS DOthey detect the wave after passing through the earth
- 66what are ELECTROMAGNETIC WAVEStransverse waves that transfer energy from a SOURCE to an ABSORBER.
they do not need a MEDIUM so they can travel through a VACUUM, and they all travel at the SAME speed in a VACUUM: 300.000.000 m/s - 67what is a spectrumif we pass WHITE light through a prism it splits into a SPECTRUM.
each light has a different frequency and wavelength.
it starts with low frequency but long wavelength - 68explain the SPECTRUMred, orange, yellow ,green, blue, indigo and violet.
radio, microwave, infrared, visible light, ultraviolet, x rays, gamma rays.
visible light is the only wave that our human eye could detect. - 69why is a spectrum defined continuousthe cut off point between a type of wave and another is NOT clear.
- 70in what depends what happens to a waveit depends on the WAVELENGTH :
microwaves are absorbed by food that contains water molecules and it is reflected by metals.
light waves are absorbed by black surfaces and reflected from shiny and metallic surfaces - 71explain the refraction of wavesthe waves can change direction if the speed changes moving from a medium to another
- 72draw and explain the ray diagram of refractionwhen the light passes from air to glass the velocity of light decreases and when it slows down it bends towards the normal and pass through the glass block, and when the wave passes back to the air their velocity increases and bend away from the normal and so the image will appear to have shifted positions
- 73what happens if the waves enters or leaves the medium at right anglesthe wave do not change direction
- 74what is meant by wavefrontimaginary line that connects all the same points in a set of waves.
makes it easier to visualise lots of waves moving together
- 75how can you use wavefront to explain refractionwe remove the wave diagram and leave just the wavefront
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- GCSE Physics Fichas sobre topic 5, creado por Vanessa pacchia el 09/04/2023.
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- Vanessa pacchia
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