Karteikarten
4.4 Waves
Karten in diesem Stapel (31)
- 1what is a longitudinal wave?a type of wave where the vibrations are along the direction of travel
- 2what are transverse waves?these are waves that are perpendicular to the direction of travel
- 3whats the displacement of a wave? Amplitude?how far from a point a wave has moved.
Amplitude- maximum magnitude of displacement - 4what is the wavelength? what is the period?WL: The length of one whole wave cycle. e.g from crest to crest
Period: time taken for a whole cycle to complete - 5what is phase difference? what is frequency?PD: the amount one wave lags behind another
Freq: the number of cycles per second passing a given point. its the inverse of period - 6technique to work out frequency of wave?work out the period, which will be shown on the oscilloscope.
count the number of squares taken by one cycle. find the seconds per box division.
Multiply the number of boxes by ms/div for period
freq = 1/period.
use this, converting time to seconds - 7equation for speed?v = distance/time
v = wavelength * frquency - 8graphically representing waves?transverse: using displacement (y) against distance (x) or displacement against time
longitudinal: using displacement against time - 9what is reflection?the process of a wave bouncing back after hitting a boundary. incidence angle always equal reflection angle.
- 10what is refraction?refraction is the change in direction of a wave as it enters a different medium.
this is because the wave speeds up of slows down
if wave bends away from medium, speed up. towards medium, slow - 11what is polarisation?Polarisation is the production of waves oscillating in one plane (ie with one line of oscillation) from a source of randomly oscillating waves.
the plane of oscillation is called the plane of polarisation - 12what is diffraction?the process by which waves spread out after coming out of a narrow gap. the smaller the gap, the greater the diffraction.
- 13ripple tank for experimentFor diffraction:
fill up a tank with shallow amount of water.
place in a oscillating paddle, which continuously vibrates, creating evenly distributed waves, straight and parallel wave fronts
.Place an object in the tank to create a barrier that has a hole in it.
change the size of the gap to see the effect of diffraction - 14techniques to show polarising light?Shine unpolarised white light into two polarising filters
align the transmission axis on the two filters so that they are both vertical.
Light passing first filter is vertically polarised. at perfect alignment, light passing trough first filter will pass second filter
rotating second filter will vary light
at 45 degrees, half light, at 90, no light - 15what is the intensity of a progressive wave?intensity ∝ (amplitude)^2
- 16the electromagnetic specturm properties?all waves in a vacuum travel at 3x10^8 ms
the are all transverse with electric and magnetic field. the fields are perpendicular to travel direction - 17the order of the electromag spec?smallest wavelength to largest :
Gamma
Xray
UV
Vis light
IR
Micro
Rad - 18what is the refractive index?Refractive index of material measures how much it slows down light
index(n)=speed in vacumm/speed in new material. the speed of light in air is only a bit smaller than air so it can be assumed n for air is 1 - 19what is snells law?snells law states that the product of the index and the sin of incident ray is equal to the product of "n" and sin of refracted ray (n(sin) angle 1)=(n(sin)angle2)
- 20experiment for refraction?.Place glass around water and draw around it
.use ray box to shine beam of light into block.
turn off other lights to see the path.
.trace path of incoming and outgoing rays .
remove block and connect line with straight line.
Measure incidence and refractive ray. when entering glass, should bend towards normal. - 21investigation of total internal reflection?shine a ray of light into curved surface of glass semicircle block, so that it doesnt refract.
increase incidence angle until output ray shines along straight edge. critical angle.
increase incidence so that it is greater than critical angle, this is total internal ref - 22formula for TIR?sinC=1/n
- 23what is principle superposition?when two or more waves cross, the resultant displacement is vector sum of individual displacements.
- 24techniques for superpositionconnect two speakers to the same oscillator. and place them in line with one another. walk slowly across the room in front of them.
where its loudest, the path difference is a whole wavelength.
where its quietest, its an odd number of half wavelengths. - 25what is interference and coherence?interference:
when two waves superpose the affect is called interference.
Coherence:
when two waves the same wavelength and frequency and have a fixed phase difference. - 26Path difference:amount by which one waves travelled path is longer than the other.
- 27constructive and destructive interference?constructive wavelength occurs when two waves are at equal distance from source. or when path difference is a whole number of wavelengths
destructive: when waves are in antiphase and they cancel eachother out as a resultant. amplitude=0 - 28demonstrating two source interference?have coherent sources so that wavelength and frequency is equal. for sound, connect one oscillator to two speakers
for microwaves: connect microwave cones to the same signal generator. use microwave probe as screen. move screen and get alternating signals - 29what is youngs double slits? and the formulasan experiment that proved light was a wave that could diffract and interfere.
fringe spacing = (wavelength*distance)/ space between slit
wavelength= (fringe spac*spac slits)/D - 30finding wavelength of light using diffraction grating and double slitsdouble slits. shine light through double slits. they have to be same length as wavelength so diffraction takes place. coherent sources. pattern of dark fringes. wavelength is fringe spacing
- 31with diffraction gratings for light?shine monochromatic light into grating, hundreds of slits per milimetre. interference pattern is sharp because more beams reinforce the pattern.
because fringes are sharper, measurements are more precise. they are easier to tell apart
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- A level Physics (Unit 4: Electrons, waves and photons) Karteikarten am 4.4 Waves , erstellt von Daniel Nnajiuba am 13/03/2019.
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- Daniel Nnajiuba
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