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Module 4 - Chapter 11 - Waves 1 I - Coggle Diagram
Module 4 - Chapter 11 - Waves 1 I
Progressive waves
Wave that transfers energy from place to another with a wave front which travels through the material
Particles in the matter vibrate, they don't move along the wave
Transverse waves
Osciallations are perpendicular to the direction of energy transfer
Have peaks and troughs where particles are at a maximum displacement from their equilibrium position
Longitudinal waves
Oscillations are parallel to the direction of energy transfer
Create a series of compressions and rarefractions
Properties
Displacement - distance from equilibrium position
Amplitude - Maximum distance of the wave from its equilibrium position
Wavelength - minimum distance between two points in phase on adjacent waves
Period - Time taken for one osciallation, or for one wave to move one whole wavelength past a given point
Frequency - number of wavelengths passing a given point per unit time
Wave speed - distance travelled by the wave per unit time
Graphs
Displacement-distance graphs
Used to determine the wavelength and amplitude of both types of wave
As displacement of the particles in the wave is continuously changing, wave profile changes shape over time
Wave profile
Displacement time graphs
Shows the dsplacement of a given particle as the wave passes through the medium
Looks the same for transverse and longitudinal waves
Used to determine the period and frequency
Intensity
If power of wave source is known ,the drop in brightness can be used to calculate how far the source is from the receiver
Radiant power transmitted by a wave per unit area
Intensity and distance
Intensity of a wave depends on the area over whcih the power is spread out
For any point source of a wave, energy and power spread uniformly in all directions over the surface of a sphere
Intensity and amplitude
Decreased amplitude means decreased average speed, halving the amplitude mean particle oscilate with half the speed and a quarter the kinetic energy
Reflection
Wave changes direction at a boundary between two different media, remaining in the original medium
angle of incidence = angles of reflection
When waves are reflected, their frequency and wavelength don't change
Refraction
When a wave bends at a boundary between two materials due to the difference in density causing it to speed up or slow down
When a wave refracts, there is always some reflection off the surface
Slows down = refracts towards the normal
Speeds up = refracts away from normal
Refraction affects wavelength but not frequency
When water waves enter shallow water, they slow down and the wavelength gets shorter
Diffraction
When waves pass through a gap or around an obstacle, they spread out
Maximum diffracton occurs when the size of the gap is the same size as the wavelength
Speed wavelength and frequency don't change
Oscilloscope
Show variation of Voltage with time
Turning off time base causes trace to show all possible voltages at any time in one area
Direct current
Trace shows a straightline parallel to axis at heigh of voltage
If time-base turns off, only a dot is shown on the screen at same height
Alternating current
Repeating sinusoidal waveform
Switching off timebase causes a strigh line to appear on the screen, showing all possible voltages
Grid
Ocilloscope has fixed grid on its display, you can adjust the scale of both axes
To change y axis, select number of volts per division using a Y-gain control
To change the scale of the X axis, adjust the timebase
Cound number of divisions and multiply by either volts per division or time base
Time period
Count number of squares between adjacent peaks
Take the inverse to find the frequency
Multiply by the time base
Voltage
Multiply by the Y gain
Count number of squares between the peak and the equilibrium line
