Waves

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wave

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any‘wiggle’, any vibration (or oscillation), that can travel from one place to another

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propagating

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when waaves move they are said to be propagating

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radiation

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any disturbance that propagates outwardly from its source. Any waves are basically forms of radiation

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energy

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the ability to move an object, All waves con do this so all waves carry energy

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oscillation

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when molecules move up and down but carry energy in a horizontal direction by passing the energy from one molecule to the next and give the appearance of moving forward

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circular oscillation

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Water waves are special and move in a circular motion rather than up and down, The circular motion gets more noticeable as you reach the surface as they are more free to move

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1D waves

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whenthe wave propagates in one direction (a line), for example up and down

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2D waves

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When waves propagate in a circular motion, can happen with anything that moves across a surface like when you drop a pebble in water

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3D waves

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Waves that travel in all directions for example someone talking travels outward spherically (in all directions)

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medium

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anymaterial with elasticity (the ability to bounce back after being disturbed)

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mechanical waves

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waves that need a medium to travel through The material that the wave is moving through usually doesn’t move with the wave but the particles oscillate staying in the same spot while the wave propagates across a distance

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sine wave diagram looks like...

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The highest point in a sine wave is a peak/crest and the lowest points are troughs.

To draw a sign wave on a graph, the y-axisx represents the displacement of the particles in the wave and the x-axis represents the direction of the wave

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transverse wave

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the particles of the medium move (displace) at right angles to the direction of wave propagation, e.g. waves on a rope.

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longitudonal wave

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The particles of the medium move (displace)along the same direction as the wave propagation, like sound waves the arrangement is compresses (pressure increase) and then expanded (pressure decrease) repetitively (also called rarefraction)

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amplitude

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themaximum distance a particle oscillates from its equilibrium position, shown inthe y-axis

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wavelength

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the distance between two peaks or similar positions on the wave. The symbol is λ (lambda)

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equilibrium position

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thex-axis of the wave showing what it would look like without disturbance

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frequency

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he number of wavelengths that pass a point per second. The unit for frequency is Hertz (Hz)

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period

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The number of seconds between two adjacent peaks or troughs (the time taken to complete a wavelength) is a period (T)

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equaion for frequency

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f = 1/T

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equation for speed of a wave

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v = λ f where v is thespeed in metres per second (m s-1), f is the frequency in Hz, and λ the wavelength in metres (m)

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two reasons why waves lose energy

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While it moves it reaches boundary's, its reflected, transmitted, and absorbed The mathematical representation of a wave as it oscillates and loses energy. The energy of a wave is Ewave ∝ Amplitude^2

or intensity

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intensity

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The rate of energy transfer by a source of waves through a given area Measured in whats per square meter (Wm-2) The equation is

intensity = power/area or I=P/A

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inverse square law

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intensity of illumination produced by a point source varies inversely as square of the distance from the source

Equation is E=I/d^2

Can't be used for most things because energy is lost while traveling through the medium but it works well for EM waves

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EM waves

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an oscillating magnetic and electric field propagating together at the speed of light

They are transverse waves because the electric and magnetic field are at right angles to each other and the direction of propagation

They travel fastest in a vacuum because there is nothing to absorb or distort the energy

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refracive index

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n=c/v

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electromagnetic spectrum

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all the possible forms of an EM wave according to the only thing that changes which is the frequency e.g. microwaves, infra-red (IR), visible light… As the wave length of EM waves increases the frequency decreases and vice versa, they are inversely proportional.