Waves
Waves and Their Characteristics
Vocabulary
Pulse - a single disturbance to the medium that moves from one place to another.
Wave - a repeating disturbance that moves from one place to another.
Medium - a substance or object that carries a wave. Ex. Water, slinky.
Transverse wave - a wave in which the particles of the medium move perpendicular to the direction of the way the wave moves.
Longitudinal Wave - A wave in which the particles of the medium move parallel to the direction the wave moves.
Electromagnetic wave - a wave capable of transmitting without a medium. Ex. Light waves
Mechanical waves - a wave that requires a medium to transmit. Ex. Water wave
Compression point - the point on medium through with a longitudinal wave is travelling that has the maximum density (the particles are closest together).
Rarefraction point - the point on a medium through which a longitudinal wave is travelling with the minimum density (the particles are furthest apart).
Amplitude - the maximum amount of displacement from the rest position, or the height of the wave.
Crest - the highest point on the wave from the rest position (points A, E, H).
Trough - the lowest point on the wave from the rest position (point C).
Wavelength - a completed cycle of a wave (from points D to G, or A to E etc.).
Period - the time it takes for a particle on a medium to complete one vibrational cycle, or one wavelength. It is measured in a unit of time, usually seconds.
Frequency - how often the particles of the medium vibrate when a wave passes through the medium, or how many wavelengths per second. It is measured in Hertz (Hz) where 1Hz = 1 cycle/second.
Formulas
Lab Summary- Waves (Slinky) Part I
In this lab we experimented with slinkys and how they carry waves. This helped us to discover the characteristics of waves such as how speed, wavelength, amplitude and frequency affect each other. Because all our findings were simply by observation, we did not always come to the correct theoretical conclusions. The theoretically correct observations are:
- Amplitude does not affect the speed (velocity), frequency or wavelength.
- The speed is only affected by wavelength or frequency (as in the universal wave equation).
- As a pulse travels through a medium the amplitude will decrease, such as how a sound wave will die out.
- The relationship between frequency and wavelength is an inverse relationship.
- The speed of a pulse does not change as it travels along a medium.
- When two pulses meet, they pass through each other.
Principal of Superposition
When two waves interact with each other the resulting wave is the algebraic sum of the original amplitude.
Ex. If a wave that has an amplitude of 4 m meets a wave with an amplitude of -6 m, the wave that occurs when they meet will have an amplitude of -2 m.
Lab Summary- Waves (Slinky) Part II
A closer look at fixed-end and free-end reflection
This lab focused specifically on reflection with fixed and free-end mediums, as well as when there is a change of medium along which a wave travels. About fixed and free-end waves, we discovered:
Standing Waves
If the medium used to create these standing waves was 100 cm long and there are two wavelengths, then one wavelength is 50 cm long.
With a standing wave, take half of the number of crests to find how man wavelengths it has. In the diagram there are four crests, so you have two complete wavelengths.
Universal Wave Equation
This lab was about using the universal wave equation and the relationships between each of the variables. We discovered that velocity (v) is a constant and frequency (f) and wavelength have an inverse relationship. This means that if frequency decreases, wavelength will increase and vice versa. Wavelength symbol is lambda.
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