Physics Preliminary Course Overview

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Physics Preliminary

8.2 The World Communicates

1. The wave model can be used to explain how current technologies transfer information

1. Describe the energy transformations required in one of the following: – Mobile telephone
– Fax/modem
– Radio and television
A. An energy transformation is a change in the type of energy, for example a change from sound energy to electromagnetic waves. Relating this to the mobile telephone, it undergoes basic energy transformations of, sound wave (your voice), to electrical energy (in the wires inside the phone), to electromagnetic waves (from the phone to the tower), to electrical energy (at the tower), then to electromagnetic waves (to reach the receiving phone), then electrical energy (inside the receiving phone), then to sound waves (at the speaker of the receiving phone)

2. Describe waves as a transfer of energy disturbance that may occur in one, two or three dimensions, depending on the nature of the wave and the medium A. Waves carry energy and sometimes they require a medium and sometimes they don’t. Laser lights are an example of a 1 Dimensional wave, water waves are an example of a 2D wave while an example of 3D waves is a sound wave

3. Identify that mechanical waves require a medium for propagation while electromagnetic waves do not A. Mechanical waves, such as sound waves, water waves and earthquake waves need a medium (a substance) to travel through, they cannot move from one point to another if there is nothing (a vacuum) between the two points. On the other hand electromagnetic waves do not need a medium to travel through. An example of this is in space, which is a vacuum, if you call out in space your sound waves do not penetrate out of your space suit. However electromagnetic waves do, therefore you can see the light from the sun. Even simpler, in space you can see a planet explode, but you cannot hear it.

4. Define and apply the following terms to the wave model: medium, displacement, amplitude, period, compression, rarefaction, crest, trough, transverse waves, longitudinal waves, frequency, wavelength, and velocity A. Mechanical Waves: The group of waves that required a medium for transmission, e.g. sound waves Electromagnetic Waves: The group of waves that do not require a medium for transmission i.e. ultraviolet light, visible light etc. They all travel at the same speed in a vacuum, which is the speed of light. Transverse Waves: Waves in which the particles oscillate at right angles to the direction of motion of the wave, e.g. surface water waves. Direction of Propagation: The direction of motion of a wave

Longitudinal Waves: Waves in which the particles oscillate parallel to the direction of motion of the wave e.g. sound. Periodic Waves: Wave disturbance that repeat themselves at regular intervals. Compressions: Regions of a longitudinal wave where the particle are close together. The point where the medium has a maximum density Rarefactions: Regions of a longitudinal wave where the particles are spread apart. The point where the medium has a minimum density. Crest: The point of a wave where the particles of the medium have a maximum displacement upwards or in a positive direction. Trough: The point of a wave where the particles of the medium have a maximum displacement downwards or in a negative direction Amplitude: The maximum displacement of the particles of a medium from their rest position Wavefront: An imaginary line joining any group of adjacent particles that are in a phase with each other. Wavelength: The distance between any two corresponding points of a wave Frequency: the number of waves that pass a point in one second Period: Number of crest passages per unit time.

5. Describe the relationship between particle motion and the direction of energy propagation in transverse and longitudinal waves A. Particles in the medium move in a direction perpendicular to the motion of transverse wave. Particles in the medium move in a...
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