Applied science

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Basic waves section one :

Displacement - The distance a wave moves a partial from its rest position

Amplitude - The maximum displacement

Wavelength- The distance between two similar points on the wave

Period time or period, (s) - The time between two similar events

Frequency (Hz) - The number of complete cycles per second

Frequency = 1/Time ( Period) or Time = 1/ Frequency

Transverse wave - The displacement is at a right angle to the wave direction. The waves move up and down

Longitudinal wave - The displacement is parallel to the wave direction . The waves move back and forth.

Units :

Giga (G) - 1000,000,000 x10 (9)

Mega (M)- 1000,000 x10 (6)

Kilo (K) - 1000 x10 (3)

Milli (m) - 0.001 x10 (-3)

Micro (,u)- 0.000001 x10 (-6)

Nano (n) - 0.000000001 x10 (-9)

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Phase

The size of a phase difference can be expressed in different ways. You can express it as :

A distance

A time difference

A fraction of a cycle

An angle in degrees ( in which one cycle id 360 degrees)

An angle in radians ( in which one cycle is 2 )

For an explore imagine two olympic runners running around a track. If two runners ran at he same time at the same speed this would mean they are in phase. If on runner was half a circuit behind due to them not being at athletic they would be completely out of phase ( 180 degrees out of phase or 1 radius out of phase.

Wave velocity (speed)

velocity(ms-1) = distance (m) D

Time (s) V|T

velocity(ms-1)= Frequency (Hz) V

Wavelength(m) F|WL

Musical note

Musical mote have three characteristics :

Pitch - to describe how high or low a note is , this depends on the frequency of the wave ( the higher the frequency the higher the pitch)

Loudness - this depends on the amplitude of a wave ( the bigger the amplitude the more energy the sound wave contains there the sound is louder.

Quality (tone)- the quality of a note depends on the wave form. The same note from different instruments has different qualities because the sound from from instruments are never pure notes.

A tuning fork produces a single repetitive wave form. a musical instrument consist of one main note which is predominant and other smaller notes called overtones . noise waveform is the hiss you hear from a radio or TV is not tuned is caused by the waveform is not repetitive.

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Standing waves in strings

A standing wave is a vibration of a system where some particular parts remain fixed where as the other vibrate to the maximum amplitude. At fixed ends they have no movement there fore they have zero displacement. When the wave hits the fixed point it is reflected back allowing it to travel back and fourth in opposite directions.

The waves travel back and forth can be added together to show a single wave. At the reflecting surface the two waves are equal and opposite - so they cancel each other out , this is a Node. at other parts along the wave they add together to made a double size wave, this is an Anti-node. The distance between two nodes or two antinodes is half a wavelength. where as the distance between a node and an anti-node is one quarter of a wavelength.

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The first fundamental frequency is the lowest frequency and is only 1/2 wave length. to get to the second harmonic the frequency in increased and the wavelength in decreased is means the wavelength in one quarter. overall showing 1 wavelength in the same space provided. The third harmonic has the highest frequency of the three and the lowest wavelength of 1/3. in the same space it shows one and a half wavelengths.

The wave length of the wave = length of the string / number of complete waves.

progressive waves are different from standing waves as progressive waves as all points along the wave have the same amplitude and transfers energy from one place to another however not all points are in phase , on the contrary the standing wave all points have different amplitude as well as no energy transfer , between two nodes on the standing wave are in phase.

Standing waves in Pipes

woodwind instruments create standing wave, as they have one or two open ends to the pipes this forms an Node at the closed end and an anti-node at the open end of the pipes, by opening and closing the holes this effects the length of the pipe .

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Polarisation

Only waves such as light, microwaves and radio waves can be polarised. This is due to the waves being transverse , Transverse waves can be polarised due to the movement being at a right angle to the direction of propagation. Longitudinal waves can't be polarised , for example sound tis is due to the oscillation only occurring in one direction.

A wave that oscillates in every direction at once is called un-polarised.A wave that only oscillates in one direction is called polarised.

Polarised wave - A wave where the displacement is only in one possible transverse directions.

Light waves can be polarised by passing through a special material for example a polaroid filter. this filters are also used in sunglasses and photography lenses.

Microwave can be polarised using metal bard instead of a polaroid filter.

Radio and television transmissions are polarised as well these are revives by mounted ariels that are mounted either horizontal or vertical. This is due to the arial pointing towards the transmission signal and are lined up in the same direction as the transmission this reduces chances of interference.

Reflected light light that is reflected off the surface can be polarised if there is a large enough concentration of light in one place. This can be carried out of surfaces including waters surface however this is not possible on metallic surfaces.

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