AS Physic Unit 2 Waves
- Created by: Rebecca Kneath
- Created on: 22-01-18 09:38
View mindmap
- Waves
- The nature of waves
- Progressive wave
- A pattern of disturbances travelling through a medium and carrying energy with it.
- It involves the particles of the medium oscillating about equilibrium position.
- It does not involve the transfer of matter.
- Transverse Waves
- Particle oscillations are at right angles to the direction of travel of the wave.
- Example of a transverse waves is light.
- Longitudinal waves
- The particles oscillations are parallel to the direction of travel of the wave.
- An example of a longitudinal wave is a sound waves.
- Displacement - distance graph is a snapshot of the wave at a particular time.
- A displacement-time graph follows the movement of one particle over a given time.
- Characteristic
- Wavelength
- the minimum distance between two points on the wave oscillating in phase.
- Frequency
- the number of cycles of a wave that pass a given point in one second
- Amplitude
- distance from the middle of the wave to the crest
- Speed
- the distance traveled by the wave one second
- Wavelength
- Phase
- The relationship between the pattern of vibration of two points on a wave.
- Points oscillating in phase will be multipliers of 360
- Points oscillating in anti phase will be 180 out of phase.
- Wave Equation
- Speed = frequency x wavelength
- Speed is in ms Frequency is in Hz Wavelength is in m
- Speed = frequency x wavelength
- Polarization
- A transverse wave in which the particle oscillations occur in only one of the directions at right angles to wave propagation.
- If you try to view polarized light through a second polarizer filter rotating 360 the what you would see would be alternating light and dark.
- Progressive wave
- Wave poperties
- Reflection
- As the waves strike a plane barrier they are reflected. This is very similar to a beam of light reflecting on a plane mirror.
- If a cruve barrier is used, the waves can be made to converge at a point. the angle of incidence is equal to the angle of reflection.
- Refraction
- the change in direction of a wave at a boundary between two materials. This is caused by the change in speed.
- Diffraction
- The spreading out of a wave when it meets an obstacle into regions where it would not be seen if it moved only in straight lines.
- principle of Superposition
- If the waves from two sources occupy the same region then the total displacement at a point is the vector sum of the displacements of the individual waves at that point.
- there are two types of interference when this takes place. Constructive and Destructive interference.
- Constructive Interference - if two waves arrive at a point in phase, have the same frequency and equal amplitude.
- destructive Interference - if the peak of one wave arrive at the same time as the toughs fro the other. There will be a smaller amplitude and sometimes cancel out
- Coherence
- There is a constant phase difference and same frequency.
- An example is a laser light.
- Path Difference
- A measure of the distance between two waves arriving at a point in terms of their wavelength.
- If we consider the effect of superposition at many points, an interference pattern will develop showing areas with constructive and destructive interference.
- if the path difference is S2P - S1P equals a whole number of wavelengths then the waves arriving at point P in phase will produce constructive interference
- If S2P - S1P is equal to multipliers of half wavelengths then waves arriving in anti-phase at point P will produce destructive interference.
- Young's Double Slit Experiment
- Two light sources at the double slits are produce. Because these two light sources originate from the same primary source, they are coherent and create an interference pattern.
- Bright fringes can be created when the diffracted waves overlap and are caused by constructive interference.
- Dark fringes can also be created from destructive interference.
- The diffraction grating
- Its a plate on which there are a very large number of parallel, identical and closely spaced slits.
- If monochromatic light is incident n this plate, a pattern of narrow bright fringes are produces.
- As there are many slits, the bright fringes are extremely narrow, and usually much further apart than the double slit experiment.
- dsin0 = n
- d = slit width n= order number = wavelength 0 = angle
- A very small d makes the orders much further apart and a large number of slits makes the beams much brights and sharper.
- With white light
- Each wavelength making up the white light is diffracted differently. Red is diffracted the most and violet is diffracted the least.
- Reflection
- The nature of waves
Comments
No comments have yet been made