Killina Presentation Secondary School

Optics, Waves, Sound and Light

A Real Image is an image formed by the actual intersection of light rays.

A 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 .

A Transverse wave is a wave where the direction of vibration is perpendicular to the direction in which the wave travels.

A 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.

A 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.

The Doppler Effect is the apparent change in the frequency in of a wave due to the motion of the source of the wave.

The 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.

The 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.

The 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.

A 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.