Progressive and Stationary waves

• Frequency is the number of waves passing through a point per second (hertz) Hz.
• Wavelength is the distance between two adjacent peaks on a wave.
• Amplitude is the maximum displacement of the wave from its equilibrium position.
• Time period of a wave can be found using its frequency, T = 1/f.
• Phase difference is the amount a particle or wave lags behind another particle or wave, measured in radians, degrees or fractions of a cycle.
• A longitudinal wave is a wave in which the oscillation of the particles is parallel to the direction of energy transfer, with rarefactions (areas of low pressure) and compressions (areas of high pressure).
• A transverse wave is a wave where the particle oscillations are perpendicular to the direction of energy transfer, for example: electromagnetic waves.
• Electromagnetic waves travel at 3 x 10^8 m/s in a vacuum.
• The magnetic field and electric field in an electromagnetic wave are at right angles to each other.
• A polarising filter only allows oscillations in one plane.
• TV and radio signals are usually plane-polarised by the orientation of the rods on the transmitting aerial, so the receiving aerial must be aligned in the same plane of polarisation to receive the signal at full strength.
• Where the waves meet completely out of phase, destructive interference occurs and nodes (regions of no displacement) form.
• Where the waves meet in phase, constructive interference occurs so antinodes (regions of maximum amplitude) form.
• The conditions for a stationary wave to be produced are: the waves must be of the same frequency, wavelength and amplitude, and they must be travelling in opposite directions.
• A stationary wave is formed from the superposition of 2 progressive waves, travelling in opposite directions in the same plane, with the same frequency, wavelength and amplitude.
• An antinode is a point on a stationary wave with maximum displacement.
• A stationary wave is a wave which transfers no energy and whose positions of maximum and minimum amplitude are constant.
• The first harmonic for a stationary wave with two closed ends consists of 2 nodes at either end and an antinode in the middle.
• Polarisation can only occur if a wave’s oscillations are perpendicular to its direction of travel, as they are in transverse waves.
• A node is a point on a stationary wave where the displacement is 0.