Waves transfer energy by creating vibrations (oscillations).
If the oscillation is perpendicular to the direction of energy transfer, the wave is transverse.
If the oscillation is parallel to the direction of energy transfer, the wave is longitudinal.
Light sources like stars, light bulbs or candle flame produce transverse waves which can travel through transparent matter as well as vacuum by creating a disturbance (vibration, oscillation) in its electrical and magnetic fields.
Light travels at a speed of 300, 000,000 m/s.
Sound waves are mechanical waves and need a medium (like solid, liquid or gas) to transfer energy.
Sound waves cannot travel through a vacuum.
Some mechanical waves like ocean waves are transverse because water and salt molecules oscillate at right angles to the direction of the wave.
All waves have certain characteristics like wavelength, frequency and amplitude (see slide below).
Frequency is the number of wave cycles produced per second. For example 1 Hz = 1 cycle / s
Speed of wave = speed at which it transfers energy = frequency of wave x its wavelength
This is known as the wave equation and is written as :
v = f x l