Flashcards
Waves
Flashcards do conjunto (22)
- 1Progressive WavesTransfer energy without transferring material and is made up of particles of a medium oscillating
- 2How are points on a wave in phaseIf they are both at the same point of a wave cycle, they will have the same displacement and velocigty and phase difference a multiple of 360 degrees.
They don't need to have the same amplitude or wavelength - 3Polarised WavesOscillate in only one plane and can only be transverse. They provide evidence for transverse waves as polarisation can only occur if waves oscillations are perpendicular to direction of travel
- 4Polaroid SunglassesThey reduce glare by blocking partially polarised light as they only allow oscillations in direction of the filter which makes it easier to see
- 5SuperpositionThe displacements of two waves combine as they pass each other resulting in the vector sum of each wave's displacement.
- 6Constructive & Destructive InterferenceConstructive-Occurs when waves have displacement in same direction
Destructive- Occurs when waves have displacement in opposite directions. If equal but opposite, total destructive interference occurs - 7Stationary WavesFormed from superposition of two progressive waves, travelling in opposite directions in same plane with same frequency, wavelength and amplitude. No energy transferred by them. Where they meat in phase they constructively interfere and form antinodes. Where they meet out of phase they destructively interfere and form nodes
- 8String Example of Stationary WavesA wave travels down a string from oscillator is reflected at fixed end of string and travels back along the string causing superposition of the two waves and as they have all the same features, a stationary wave is formed
- 9The First HarmonicLowest frequency at which a stationary wave can be formed
- 10Young's Double Slit ExperimentCan use 2 sources of light or one source with a double slit. Shine coherent light through 2 slits, about size of wavelength, so light diffracts. Each slit acts as a coherent point source making a pattern of light and dark fringes. Light where light meets in phase. Dark where light meets out of phase
- 11Effect of using White Light in Young's Double SlitGives a wider maxima and a less intense diffraction pattern with a central white fringe with alternating bright fringes which are spectra with violey closest to central max and red furthest away
- 12Safety precautions when using lasersWear safety goggles
Don't shine light at reflective surface
Display a warning sign
Never shine laser at someone - 13What is diffractionSpreading out of waves when passing through/ around a gap. Greatest diffraction occurs when the gap is same size as wavelength. When gap bigger than wavelength diffraction is less noticeable and when gap smaller than wavelength, most waves are reflected
- 14What happens when monochromatic light is diffracted through a single slitForms an interference pattern of light and dark fringes. It has a bright central fringe, which is double the width of all other fringes and then alternates dark and bright either side. As distance from centre increases, intensity of fringes decreases
- 15What is a diffraction gratingA slide containing many equally spaced slits very close to each other. When monochromatic light shone through it, the interference pattern is much sharper and brighter than it would be passing through a double slit, due to their being more rays of light reinforcing pattern.
- 16RefractionOccurs when a wave enters a different medium causing it to change direction. For refraction of light we use Snell's law. As light crosses boundary between materials, its speed changes, changing its direction. From higher to lower optical density it will bend away from normal. From lower to higher, it will bend towards the normal
- 17Critical angleAs angle of incidence increased, the angle of refraction increases until it gets closer to 90 degrees. When angle of refraction is 90 degrees and light reflected along boundary, the angle of incidence has reached its critical angle
- 18Total internal reflectionOccurs when angle of incidence is greater than the critical angle. This is useful for optical fibres.
- 19What are optical fibresFlexible, thin tubes of plastic/ glass which carry information in form of light signals. They have an optically dense core, surrounded by cladding with a lower optical density which allows TIR to occur. The cladding also protects core from damage and signal degradation
- 20Signal Degradation- AbsorptionPart of signals energy absorbed by the fibre, reducing the amplitude of signal leading to a loss of information
- 21Signal Degradation- Modal DispersionLight rays enter fibre at different angles so take different paths along the fibre, leading to them taking different times to travel. Can be reduced by making core very narrow
- 22Signal Degradation- Material DispersionCaused by using light consisting of different wavelengths so travel at different speeds. Can be prevented by using monochromatic light
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- A level Physics FlashCards sobre Waves, criado por kian browne em 21-05-2024.
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- kian browne
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