Spm Note Physics Chapter 1

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6.1 What is waves?


Process of transferring energy from one location to another which is produced by an oscillating or vibrating motion.

Examples of Light waves are produced as a result of vibrations of waves electrons in an atom Sound waves are produced by vibrating mechanical bodies such as a guitar strings or a tuning fork. Water waves are produced by a disturbance on a still water surface. How do waves transfer energy? When energy is transferred by a wave from a vibrating source to a distant receiver, there is no transfer of matter between the two points. When the string is shaken up and down, a disturbance moves along the length of the string. It is the disturbance that moves along the length of the string, not parts of the string itself. Drop a stone in a quite pond. It will produce a wave that moves out from the center in expanding circles. It is the disturbance that moves, not the water. After the disturbance passes, the water is where it was before the wave was produced .

The energy transferred from a vibrating source to a receiver is carried by a disturbance in a medium, not by matter moving from one place to another within the medium

The string and water is the medium through which wave energy travels.

What is A transverse wave is a wave in which the vibration of Transverse particles in the medium is at right angle to the direction of Wave? propagation of the wave.


What is Longitudin al Waves?

The spring is moved sideways. The motion of the particles medium (spring) is at right angles to the direction in which the wave travels. Examples: water waves, light waves A longitudinal wave is a wave which the vibration of particles in the medium is along (parallel to) the direction of propagation of the wave.

The slinky spring moves backwards and forwards to produce a transverse wave. The particles of the medium (spring) move along the direction of the wave. The wave that travels along the spring consists of a series of compression and rarefaction. Examples: sounds waves.


What is a ripple tank?

The phenomenon of water waves can be investigated using a ripple tank. The water waves are produced by a vibrating bar on the water surface. The tank is leveled so that the depth of water in the tank is uniform to ensure water waves propagate with uniform speed.

The water acts as a lens to produce a pattern of bright and dark regions on a piece of white paper placed under the tank when light passes through it. Water waves have crests and troughs. A crest is the highest position of the wave acts as a convex lens, whereas a trough is the lowest position acts as a concave lens. Light rays from the lamp on top will focus onto the white screen below. The bright lines correspond to the crests, and the dark lines correspond to the troughs.


What is meant by a wavefront? Lines joining all the points of the same phase are called wavefronts.

1. Plane wavefronts

2. Circular wavefronts

The wavefronts of a transverse wave and longitudinal wave are perpendicular to the direction of propagation of the waves. Describing Waves Vibration/Oscillation The movement from one extreme position to the other and back to the same position.

Amplitude (a) The maximum displacement from its equilibrium position. Amplitude relates to loudness in sound and brightness in light. SI unit: meter, m Wavelength (λ) The distance between two adjacent points of the same phase on a wave.

The distance between two successive crests or two successive troughs

The distance between two successive compressions or two successive rarefactions in a sound wave.


Period (T) The time taken for an oscillation to complete one cycle. SI unit is second (s). Wave Speed (v) The speed of a wave is the measurement of how fast a crest is moving from a fixed point. SI unit is ms-1.

Frequency, f Relation between The number of waves frequency and period: produced in one 1 second. f = T SI unit is Hertz (Hz)...
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