Real Image – is an image formed by the actual intersection of light rays.
Virtual Image – is formed by the apparent intersection of light rays.
Refraction – is the bending of light as it passes from one medium to another.
The Refractive Index of a Medium – is the ratio of the sine of the angle of incidence to the sine of the angle of refraction when light travels from a vacuum into that medium.
Snell’s law of refraction – states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant .
Transverse wave – is a wave where the direction of vibration is perpendicular to the direction in which the wave travels.
Longitudinal Wave – is a wave where the direction of vibration is parallel to the direction in which the wave travels.
Refraction – is the changing of direction of a wave as it travels from one medium to another.
Diffraction – is the spreading of waves around an obstacle.
Interference – occurs when two waves combine to produce a wave of a different amplitude.
Coherent Sources – are sources which have the same frequency and are in phase with each other.
Polarised wave – is a wave which vibrates in one plane only.
Stationary waves – are formed when two periodic travelling waves of the same frequency and amplitude travelling in opposite directions meet.
Doppler Effect – is the apparent change in the frequency in of a wave due to the motion of the source of the wave.
Natural frequency – of an object is the frequency at which the object will vibrate if free to do so.
Resonance – is the transfer of energy between two objects which have the same natural frequency.
Sound Intensity – at a point is the rate at which sound energy is passing through unit area.
The threshold of hearing – is the smallest sound intensity detectable by the average human ear at a frequency of 1 KHz.
Frequency limits of audibility – are the highest and lowest frequencies that can be heard by a normal human ear.The range is 20 Hz – 20,000 Hz.
Overtones – are frequencies which are multiples of the fundamental frequency.
Diffraction grating – consists of a piece of transparent material on which a very large number of parallel lines are engraved.
Dispersion – is the separating of white light into its different colours.