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Waves - Coggle Diagram
Waves
Electromagnetic waves
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In space, all waves have the same velocity (speed of light)
They can transfer energy from a source to an absorber
(microwave source to food, sun emits energy to earth etc)
As speed is constant for all EM waves: as the wavelength decreases, the frequency increases
As the frequency increases, the energy of the wave also increases
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Uses of EM waves and why
Radio waves: used in TV and Radio because they have a long wavelength and can travel far without losing quality
Microwaves: used for satellite communication and cooking food because they can penetrate the atmosphere to reach satellites
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Visible light: used in optic fibers because they have the best reflection to scatter glass (other waves are too short/long)
UV light: used in sun tanning and energy efficient lightbulbs because they radiate the least heat but the most energy
X-rays/gamma rays: used in medical imaging and treatment because they are very high in energy and can penetrate materials easily
Hazards
UV light, X-rays and gamma rays have effects on the human body tissue, depending on the type of radiation and the size of the dose
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UV - skin ages prematurely, increasing risk of skin cancer. However, suncream can prevent overexposure in summer
X-ray and gamma rays - ionising radiation that cause mutations of genes and cause cancer. Minimal exposure should be ensured
Wave basics
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Frequency: number of waves that pass a single point per second/number of waves produced by a source each second
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Period is inversly proportional to frequency (double one, halve one)
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Interactions
Reflection: wave will reflect off a flat surface. The smoother the surface is, the stronger the reflected wave is. Rough surfaces scatter the light in all directions so they appear matt and not reflective.
angle of incidence = angle of reflection
Light will reflect if the object is opaque and not absorbed by the material. Electrons will absorb the light energy and reemit it as a reflected wave.
Transmission: waves will pass through a transparent material. The more transparent, the more light will pass through the material. It can still refract, but the process of passing through the material and still emerging is transmission
Absorption: If the frequency of light matches the energy levels of the electrons.
The light will be absorbed by electrons and not reemitted. They will be absorbed, and then reemitted over time as heat.
That frequency has been absorbed. So, if a material appears green, it is because the green light has been reflected but the rest of the colours have been absorbed
Wavelength: the distance between the same points on 2 consecutive waves (measured from peak to peak or trough to trough)
Visible light
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Red has the lowest frequency but the longest wavelength. Violet has the highest frequency but the shortest wavelength.
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Types of reflection: Specular: smooth surface gives a single reflection
Diffuse: reflection off a rough surface causes scattering
Colour filters work by absorbing every other colour, and only letting a certain wavelength through
An opaque object has colour, determined by the strength of reflection for different wavelengths
Wavelengths which are not reflected are absorbed. If all wavelengths are reflected, it appears white. If all wavelengths are absorbed, it appears black. The wavelength that is absorbed = the colour it appears
Objects that transmit light are either transparent or transulcent (scatter most light and only let some through)
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Types of waves
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Transverse waves have peaks and troughs 
Longitudinal waves have rarefactions and compressions
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