Preliminary Physics Module 1: The World Communicates
The wave model can be used to explain how current technologies transfer information
1.1 Describe the energy transformations required in one of the following: mobile phone:
Sound waves -> electrical signals, transformed by built in microphone
These signals are digitised (turned into 1s and 0s) and are transmitted as radio waves to a base station
The base station is connects the signals to switching centres by cables
The switching centres then connect the signals to other switching centres or base stations
If, Mobile-Distant fixed telephone – signals are converted to light
If, Mobile-Fixed telephone – signals are converted to electrical impulses
If, Mobile-Mobile – signals are converted to electrical then radio waves
All are then transferred to sound waves
1.2 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 wave transfers energy from one place to another and is a vibration or disturbance
Waves may occur in one dimension (a single beam of light), two dimensions (a circular wavefront in a pond) or three dimensions (the light from a star)
1.3 Identify that mechanical waves require a medium for propagation while electromagnetic waves do not:
Mechanical waves, such as sound and water waves, require a medium to travel through
Mechanical waves can be transverse (the particles vibrate perpendicularly to the direction of energy transfer) or longitudinal (the particles vibrate parallel to the direction of energy transfer)
Electromagnetic waves, such as light and radio waves, are transverse and do not require a medium to go through as they are self-propagating because as the electrons are accelerated with atoms they generate changing electric fields, which in turn generate changing magnetic fields, which generate electric fields allowing the waves to move
1.4 Define and apply the following terms to the wave model: medium, displacement, period, amplitude, compression, rarefaction, crest, trough, transverse waves, longitudinal waves, frequency, wavelength, and velocity:
Medium – the substance in which the material is moving through
Displacement – the distance travelled by one particle in a wave from its resting position
Amplitude – the maximum size of particle displacement from the resting position
Period – the time it takes for a single wave to pass a fixed point, period (T) and frequency are related by the relationship:
Compression – areas of maximum (high) pressure in longitudinal waves
Rarefaction – areas of minimum (low) pressure in longitudinal waves
Crest – The maximum positive displacement (on a transverse wave)
Trough – The maximum negative displacement (on a transverse wave)
Transverse waves – the particles vibrate perpendicularly to the direction of energy transfer (if it travels through particles)
Longitudinal waves – the particles vibrate parallel to the direction of energy transfer
Frequency – the number of waves that pass a fixed place per second, measured in Hertz (Hz)
Wavelength – the distance between two adjacent crests and troughs (or compressions and rarefactions), measured in metres (m)
Velocity – the speed of the wave, measured in m/s, is calculated using the formula: , where V is velocity (m/s), f is frequency (Hz) and λ is wavelength (m)
1.5 Describe the relationship between particle motion and the direction of energy propagation in transverse and longitudinal waves:
Transverse waves – the particles vibrate perpendicularly to the direction of energy transfer (if it travels through particles)
Longitudinal waves – the particles vibrate parallel to the direction of energy transfer
1.6 Quantify the relationship between velocity, frequency and wavelength for a wave:
The velocity of a wave, measured in m/s, is calculated using the formula: , where V is velocity (m/s), f is frequency (Hz)
