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AS Physics- Waves
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- 1What do waves carry from one place to another?Energy.
- 2Name some wave properties1) Diffraction
2) Interference
3) Refraction
4) Reflection - 3What is the relationship between the frequency of a wave and it's time period?Frequency = 1 / time period
- 4What is the wave equation?Speed of wave = wavelength x frequency
V = λ X f - 5What are the units of frequency, displacement and amplitude?Frequency = Hz
Displacement = metres
Amplitude = metres - 6Why does light travel the fastest in a vacuum and slow down in other media?Light goes the fastest in a vacuum because it is slowed down by interacting with particles and a vacuum is devoid of matter. The more optically dense a material is, the more light slows down when it enters it.
- 7What is Snell's law?n1 sin (i) = n2 sin (r)
- 8What is the absolute refractive index?The ratio compared with the refractive index of a vacuum.
- 9What is the relative refractive index?The ratio of the absolute refractive index of one material compared to that of another, for example from water to glass.
- 10What if the formula for the absolute refractive index?n = c / v
n = absolute refractive index of a material
c = speed of light in a vacuum
v = speed of light in that material - 11What is the formula for the relative refractive index between two materials?1n2 = v1 / v2
1n1 = relative refractive index between 2 materials
v1 = speed of light in material 1
v2 = speed of light in material 2 - 12What is cladding used for?To prevent the light from escaping from the fibre and to protect it.
- 13What is an optical fibre?Allow light to "bend".
Thin flexible tube of glass or plastic that can carry light signals over long distances and round corners.
Optical fibres have a high refractive index but the cladding surrounding them has a lower refractive index. - 14What is superposition?When two or more waves pass through each other and their displacements combine. After they have passed one another they will return to normal.
- 15What is constructive interference?When either a crest and a crest superpose (forming a big crest) or a trough and a trough superpose (forming a big trough).
- 16What is deconstructive interference?When a crest and a trough of equal sizes superpose and the two displacements cancel each other out completely.
- 17What does it mean if two points are "in phase"?They will interfere constructively.
if two points are in phase, they're at the same point in the wave cycle.
2 Points that are in phase have the exact same displacement and velocity. - 18If two sources are coherent, what can you say about their frequencies, wavelength and phase difference?The frequencies and wavelengths must be equal and the phase difference will be constant.
- 19Even though two sources might be coherent, explain why it may be difficult to observe interference patterns.Interference will only be noticeable if the amplitudes of the waves are approximately equal.
- 20If two points are exactly out of phase, what are their displacements and velocities like?The displacements and velocities of the two points are equal in size but in opposite directions.
- 21What are standing waves?When a progressive wave is reflected at a boundary.
A standing wave is the superposition of two progressive waves with the same wavelengths, but moving in opposite directions.
No energy is transmitted by a standing wave. - 22At four times the fundamental frequency, how many half wavelengths can fit on a string?2 wavelengths (half of the fundamental frequency).
- 23What experiment can be used to investigate standing waves in a column of air?If a powder is laid along the bottom of a glass tube and it is shaken away from the anodes but left undisturbed at the nodes.
- 24What is diffraction?Where a wave is spread out as it passes through a slit.
- 25When the gap is the same size as the wavelength, do you get the most or least diffraction?The most
The smaller the gap, the more diffraction, however if the gap is smaller than the wavelength, the waves are mostly just reflected back. - 26What happens when a wave meets an obstacle?You get diffraction around the edges, and behind the obstacle on the other side, there's a "shadow" where the wave is blocked. The wider the obstacle, the longer the shadow.
- 27What does Young's experiment show about the nature of light?It show's its wave particle duality. It showed light as being a wave as there was an interference pattern, and if light was a particle, there wouldn't be areas of constructive and deconstructive interference (light and dark). At the screen, however, the light is absorbed as discrete particles, called photons, which demonstrates the particle nature of light.
- 28What is Young's double slit formula?Fringe spacing, X, = D λ
d - 29Describe Young's double slit experiment.You shine a light source (e.g. a laser as the light is coherent and monochromatic) through two slits.
As long as the slits are the same sized, the light will be diffracted and the light from the slits acts as two coherent sources.
You then get a pattern of dark and light fringes. - 30How is the diffraction grating pattern for white light different to that of laser light?Laser light is monochromatic (one wavelength) and the interference pattern is really sharp. If you shine white light through a diffraction grating, it produces a spectra.
- 31What difference does it make to the pattern if you use a finer grating?If the distance between the slits, d, is smaller, the pattern will be less spread out.
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- Fichas sobre AS Physics- Waves, creado por Lauren Robinson el 11/04/2015.
- Creado por
- Lauren Robinson
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