A wave is a periodic disturbance that transmit energy from one point to another.
There are two types of waves:
Transverse waves – in which the vibrations are perpendicular to the direction of wave travel. For example electromagnetic waves.
Longitudinal waves – in which the vibrations are parallel to the direction of wave travel. For example sound waves.
A wave can be described by the following properties:
Amplitude – the distance from the rest position to the peak position of a wave.
Wavelength (λ) –the distance between two similar successive points of a wave. For example, distance from peak to the next peak, or trough to the next trough.
Frequency (f) –the number of complete oscillations per second (measured in Hz).
Period –the time taken by the wave to complete one oscillation (in s).
Wave speed is the distance travelled by the wave per unit time.
All waves can be reflected, refracted and diffracted whereby,
Reflection is the bouncing of a wave off a surface.
Refraction is the bending of a wave when it crosses a boundary of two different media.
Diffraction is the spreading out of a wave when it passes through a narrow gap.
All waves obey the wave equation: v = fλ, whereby v is the wave velocity, f is the frequency and λ is the wavelength.
Sound is a longitudinal wave whose:
amplitude is related to its loudness (the greater the amplitude, the louder the sound.)
wavelength is related to its pitch (the shorter the wavelength the higher the pitch).
Sound is produced by vibrations in a medium and it needs a medium to travel.
An echo is sound reflected from smooth hard surfaces.
Ultrasound is a very high frequency sound wave that is used:
in medicine to "see" into the human body
to measure the depth of rivers
to study the earth’s crust.
Laws of reflection:
The angle of incidence is equal to the angle of reflection.
The incident ray, reflected ray and the normal all lie in the same plane.
Laws of refraction:
The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant. (Also known as Snell’s law).
The incident ray, refracted ray and the normal all lie in the same plane.
Properties of the image formed by a plane mirror:
Laterally inverted
Same distance from the mirror as the image is in front of the mirror.
Same size as the object
Virtual
Properties of refraction:
If a wave enters a more dense medium it will be bent towards the normal.
If a wave enters a less dense medium it will be bent away from the normal.
Total internal reflection is when a wave reflects off the inside of a surface when it hits the boundary at an angle greater than critical angle.
