User:Cindy9912/sandbox

WAVES Waves carry energy from one location to another. When a wave passes, each part of the waves moves away from its normal position and then returns. This is called an oscillation. Oscillations within the wave are slight movements either side of the normal position. The wave motion is the disturbance that passes through the wave. A wave pulse causes the wave to have one oscillation. A continuous travelling wave causes the wave to keep oscillating. Waves transfer energy without transporting matter because each part of the wave oscillates on the spot.A transverse pulse causes the spring to move at right angles to the direction of motion of the pulse. A longitudinal pulse causes the spring to move parallel to the direction of motion of the pulse. The direction of propagation is at right angles to the wave front. The displacement at a point is how much the wave has been displaced from its normal position. Displacements are given + or - signs depending on the direction of the displacement Amplitude is the largest distance from the normal position that the wave is displaced. The wavelength l of a wave is the distance from one point to the next corresponding point. The period T of a wave is the time in seconds that it takes one wavelength to pass by. In this time the wave will complete one oscillation. The frequency f of the wave is the number of wavelengths that pass each second.Frequency and period are reciprocals. T = 1/f. The speed of a wave is equal to its frequency times its wavelength. A displacement/position graph shows the displacement of the different sections of a medium. A displacement/time graph shows the displacement of one point of a medium as time elapses. The speed of the particles of a medium is a maximum when their displacement is zero. The speed of the particles of a medium is zero where the medium has maximum displacement. For a longitudinal wave, it has a high pressure called a compression where particles are closer than normal. For a longitudinal wave, it has a low pressure called a rarefaction where particles are further apart than normal. The particles around a compression move in the same direction as the wave. The particles around a rarefaction move in the opposite direction to the wave. The particles near a compression and rarefaction have small displacements. The particles where the pressure is normal, have large displacements.When refraction occurs, the speed and wavelength change but the frequency remains constant. When a wave travels from deep water into shallow water, sine of the angle of incidence divided by the sine of the angle of refraction is equal to the speed in the deep water divided by the speed in the shallow water. This is Snell's law. Diffraction is the change in the direction of a wave when it passes near an edge or through a gap. The greater the ratio of wavelength to obstacle or gap size, the greater the diffraction.

Standing waves are the vibrations on the spot formed by waves moving through each other from opposite directions, with the same frequency and similar amplitude. Nodes are the places which always have zero displacement. Antinodes have displacements that fluctuate between maximum positive and negative values. The nodes in a standing wave pattern are separated by half the wavelength of the waves moving through each other. A node exists at a fixed end and an antinode exists at a free end. In an air column, an antinode is at an open end and a node is at a closed end. In an air column the phase of a wave reverses when it partially reflects from an open end. In an air column the phase of a wave remains the same when it partially reflects from a closed open. In an air column, the air has zero displacement at nodes. In an air column, the displacement of the air fluctuates between two extremes at the antinodes. In an air column the displacement of the air is small near nodes and large near antinodes. In an air column, air pressure fluctuates between two extremes at nodes. There is normal pressure at antinodes. Resonance occurs when a string/air column is stimulated by a vibration with the same frequency as one of its standing wave modes of vibration. When resonance occurs, the amplitude of the standing wave is very large