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Waves - unit 2 - aqa revison material
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- 1what is the wavelength of a wave?the wavelength is the distance between adjacent particles vibrating in phase
- 2what is the amplitude of a wave?the amplitude is the maximum displacement from equilibrium position
- 3what is the frequency of a wave?the frequency is the number of waves that pass a point each second
- 4what is the time period of a wave?the time period is the time taken for a particle to do one complete cycle
- 5what is phase?phase is where two vibrations are in step so they are at the same point in the cycle at the same time
- 6what is antiphase?antiphase is where two particles are half a cycle out of phase with each other
- 7what is a wave?a wave is where one particle vibrates in a medium which sets the particles next to it vibrating in the medium producing a wave that travels through the medium transferring energy from one place to another without the transfer of material
- 8what is a transverse wave?a transverse wave is where vibrations are at right angles to the direction of propagation
- 9what is a longitudinal wave?a longitudinal wave is where vibrations are parallel to the direction of propagation of a wave
- 10what is an example of a transverse wave?electromagnetic waves
x-rays, gamma rays, ultraviolet etc. - 11what is an example of a longitudinal wave?sound waves
- 12what are three electromagnetic waves properties?travel at the speed of light
travel in a vacuum
can be polarised - 13what is polarised light?light that only travels in one direction perpendicular to the direction of propagation
- 14what is unpolarised light?light that travels in all directions perpendicular to the direction of propagation
- 15what is the function of polarising filters? give three points.polarising filters polarise light in the direction of the axis
light polarised in the direction of the axis will have no loss of intensity
light polarised at right angles to this will have zero intensity - 16give two applications of polarisationsunglasses - light reflecting off a surface is polarised horizontally so sunglasses are polarised vertically to stop glare
TV Aerials need to be in the same direction as the polarisation of the TV waves for the strongest signal - 17what is the principle of superposition?when two waves meet the total displacement at that point is equal to the sum of individual displacements at that point
- 18definition of diffraction?diffraction is where waves hit a gap or an obstacle and spread out
- 19can you explain what causes different types of diffraction?little diffraction is produced when wavelength is smaller than the gap
large amount of diffraction produced when wavelength is greater than the gap
a good amount of diffraction is produced when the wavelength and gap are the same size - 20what are the 4 features of a single slit diffraction pattern?symmetrical
central maxima is twice width of maxima either side
smaller slit = more diffraction less intense
smaller wavelength = less diffraction - 21what are monochromatic and coherent light sources?monochromatic light with same wavelength
coherent light has the same wavelength and same frequency and a constant phase difference - 224 points of safety when using goggles?do not point lasers in eyes
always where special laser safety goggles
place a warning sign on door outside
people must stand and laser below eye level - 23how are standing waves formed?a standing waves is formed when two opposing waves meet with similar amplitudes and the same frequency and superpose
- 24what is a node?a node is a point where the displacement is always zero
- 25what is an antinode?an antinode is a point where displacement is a maximum
- 26what is the difference and similarities between the particles between two nodes and the particles either side of a node on a standing wave?similarities - amplitude and frequency of the waves
differences - the phase difference is half a cycle - 27what are the 3 key differences between progressive and standing waves?energy is trapped in standing waves but it travels in progressive waves
adjacent particles in a standing wave are in phase, adjacent particles in a progressive wave are out of phase
adjacent particles in standing waves have different amplitudes. adjacent particles in progressive waves have the same amplitudes. - 28what is path difference?path difference is the difference between the distance travelled by two waves
- 29what occurs when path difference of two waves that meet is a whole number of wavelength?the two waves arrive in phase and constructively interfere to produce large amplitude
- 30what occurs when the path difference of two waves is half of a whole number of wavelengths?the waves arrive in anti-phase and destructively interfere to cancel each other out
- 31what occurs during double slit interference?laser is shone at two slits approximately 0.5mm apart, the slits diffract the light. the light overlaps each other and produces dark and bright bands of light which are equally spaced and parallel to one another
- 32what is lamder,s,w and Dlamder = wavelength
s = slit separation
w = fringe separation
D = distance between slits and screen - 33what are typical experimental values for: slit separation, fringe separation and distance between slit and screen? and how are they measured?s = 0.5mm travelling microscope to 0.1mm
w = 2mm ruler to 1mm
D = 2m to 1mm - 34can you explain the practical set up of young's slits with white light?a monochromatic light source is placed in front of a narrow slit C. two slits A and B are placed in front of slit C. the slit C must be small enough to form coherent light and diffract light over two slits A and B. the two diffractions overlap to produce dark and bright bands of equally spaced parallel lines on the sceen
- 35name 4 features of a young's slits with white light experiment which can be shown b making variable changesif the monochromatic light source is moved closer intensity of light increases
if slit separation doubles the fringe separation halves
If C is widened fringes disappear
if either slit A or B is covered it produces a single slit diffraction pattern - 36what occurs when white light is used on young's slits?white central fringe
coloured outer fringes
blue inner fringe. red outer fringe
symmetrical pattern - 37what are diffraction gratings?diffraction gratings are a large number of equally spaced parallel lines rules on glass with very small slit separation (300/mm)
- 38why are diffraction gratings better than young's slitsdiffraction gratings produce brighter and sharper fringes which can be measured more accurately giving a more accurate reading of wavelength
- 39derivefor the first order maximum the path difference is one wavelength and d is the slit separation . the angle at which the first order maxima can be seen can be used as dsin0^
- 40definition of refractionis where a wave changes speed therefore it changes direction
- 41how does light bend towards the normal or away from it?light going from a more optically dense material to a less optically dense material bends away from the normal. light going from a less optically dense material to a more optically dense material bends towards the normal
- 42what happens to light that's shone normally at a medium?light does not refract when it hits a surface normally
- 43definition of refractive indexrefractive index is the speed of light in a vacuum/ speed of light In the material
- 44what is snells law
- 45what is critical angle?the critical angle is the angle of incidence when the angle of refraction is 90 degrees going from a more optically dense material to a less optically dense material
- 46what occurs when angle of incidence is greater than the critical angle?the light totally internally reflects
- 47what is the formula for the critical angle?
- 48what occurs when angle of incidence is less that critical angle?some light is reflected and some light is refracted
- 49what occurs when angle of incidence is equal to critical angle?some light is refracted at 90 degrees and some light is reflected
- 50how are fibre optics designed to work?fibre optics have a core surrounded by cladding surrounded by a buffer.
most light enters core at an angle greater than the critical angle so most of it is totally internally reflected. - 51can you give two advantages of cladding?cladding protects the core from moisture and scratches that would allow light to escape
also cladding increases the critical angle so light with a smaller angle to the axes of the core must be sent down which decreases multipath dispersion so more information can be sent down per second. - 52what are four advantages of fibre optics in communication?they are unaffected by electrical interference so can be bundled together
fibre optics do not produce electromagnetic waves that can be tapped into
they are lighter and have a smaller volume when carrying the same information
don't need boosting as often as electrical wires so less energy loss - 53give an example of what fibre optics can be used for?endoscopy - looking down peoples throats
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- Fichas sobre Waves - unit 2 - aqa revison material, creado por Nat Waterworth el 24/02/2016.
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- Nat Waterworth
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