WAVE BASICS: REFLECTION:
Waves transfer energy in the direction of travel A wave can be absorbed, transmitted or re ected
• They have an amplitude (maximum displacement), Re ection ray diagram:
wavelength (distance between same point on 2 Angle of incidence = Angle of re ection
waves) and a frequency (no. of waves per second) • The angle of incidence is the angle between the
All waves are either transverse or longitudinal incoming wave and the normal
Transverse: • The angle of re ection is the angle between the
• oscillations run perpendicular to the direction of re ected wave and the normal
energy transfer • The normal is an unreal line that’s perpendicular
• all electromagnetic waves are transverse to the surface at the point of incidence
Longitudinal: Re ection can either be specular or di use:
• oscillations run parallel to the direction of energy • Specular: when a wave is re ected in a single
transfer direction by a smooth surface > clear re ection
• they have areas of compression and rarefaction • Di use: wave is re ected by a rough surface, as
• an example is a sound wave in air normal is di erent for each incoming ray so angle
Wave speed = Frequency x Wavelength of incident is di erent > unclear re ection
REFRACTION: VISIBLE LIGHT:
Where light waves bend and change direction as Visible light is made up of a range of colours,
they enter a new media however we can only see a small part of it
• How much it refracts depends on how much the • Each colour has its own range of wavelengths,
wave changes speed, which usually depends on ranging from violet (400nm) to red (700nm)
the density • When all of the colours are put together, it creates
• If a wave slows down, it will bend towards the white light
normal, but if it speeds up, it will bend away from Di erent objects absorb, transmit and re ect
the normal di erent wavelengths of light in di erent ways:
• The wavelength changes during refraction, but the • Opaque objects don’t transmit light and absorb
frequency stays the same some wavelengths of light but re ect others
Refraction ray diagrams: • The colour of an object depends on the
• If the angle of refraction is smaller than the angle wavelengths which are re ected
of incidence, the refracted ray bends towards the • White objects re ect all and black objects absorb
normal. However, if the angle of refraction is larger, • Transparent & translucent objects transmit light
the refracted ray will bend away from the normal & the colour depends on if transmitted/re ected
FILTERS: INFRARED RADIATION:
Coloured lters are transparent objects that All objects absorb and emit infrared radiation
absorb most wavelengths of light and just let • The hotter the object is, the more infrared
some through radiation is radiated in a given time
• A primary colour lter only transmits that colour • An object that is hotter than its surroundings emits
• If you look at a coloured objects through a lter of more infrared radiation than it absorbs in order to
the same colour, you will still see the object as that cool it down
colour because it would be re ected o the object • An object that is colder than its surroundings
• However, if the object was a di erent primary absorbs more infrared radiation in order to heat
colour to the incoming light, the object would itself up
appear to be black as all of the re ected light • Objects at a constant temperature emit infrared
would be absorbed by the lter radiation at the same rate as it absorbs it
• On the other hand, lters that aren’t primary • Some colours and surfaces absorb and emit
colours let the wavelengths of like for that colour radiation better than others. E.g. a black matt
through, as well as the primary colours that are surface is the best absorber and emitter, whereas
combined to make that speci c colour a shiny white surface is the worst
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Waves transfer energy in the direction of travel A wave can be absorbed, transmitted or re ected
• They have an amplitude (maximum displacement), Re ection ray diagram:
wavelength (distance between same point on 2 Angle of incidence = Angle of re ection
waves) and a frequency (no. of waves per second) • The angle of incidence is the angle between the
All waves are either transverse or longitudinal incoming wave and the normal
Transverse: • The angle of re ection is the angle between the
• oscillations run perpendicular to the direction of re ected wave and the normal
energy transfer • The normal is an unreal line that’s perpendicular
• all electromagnetic waves are transverse to the surface at the point of incidence
Longitudinal: Re ection can either be specular or di use:
• oscillations run parallel to the direction of energy • Specular: when a wave is re ected in a single
transfer direction by a smooth surface > clear re ection
• they have areas of compression and rarefaction • Di use: wave is re ected by a rough surface, as
• an example is a sound wave in air normal is di erent for each incoming ray so angle
Wave speed = Frequency x Wavelength of incident is di erent > unclear re ection
REFRACTION: VISIBLE LIGHT:
Where light waves bend and change direction as Visible light is made up of a range of colours,
they enter a new media however we can only see a small part of it
• How much it refracts depends on how much the • Each colour has its own range of wavelengths,
wave changes speed, which usually depends on ranging from violet (400nm) to red (700nm)
the density • When all of the colours are put together, it creates
• If a wave slows down, it will bend towards the white light
normal, but if it speeds up, it will bend away from Di erent objects absorb, transmit and re ect
the normal di erent wavelengths of light in di erent ways:
• The wavelength changes during refraction, but the • Opaque objects don’t transmit light and absorb
frequency stays the same some wavelengths of light but re ect others
Refraction ray diagrams: • The colour of an object depends on the
• If the angle of refraction is smaller than the angle wavelengths which are re ected
of incidence, the refracted ray bends towards the • White objects re ect all and black objects absorb
normal. However, if the angle of refraction is larger, • Transparent & translucent objects transmit light
the refracted ray will bend away from the normal & the colour depends on if transmitted/re ected
FILTERS: INFRARED RADIATION:
Coloured lters are transparent objects that All objects absorb and emit infrared radiation
absorb most wavelengths of light and just let • The hotter the object is, the more infrared
some through radiation is radiated in a given time
• A primary colour lter only transmits that colour • An object that is hotter than its surroundings emits
• If you look at a coloured objects through a lter of more infrared radiation than it absorbs in order to
the same colour, you will still see the object as that cool it down
colour because it would be re ected o the object • An object that is colder than its surroundings
• However, if the object was a di erent primary absorbs more infrared radiation in order to heat
colour to the incoming light, the object would itself up
appear to be black as all of the re ected light • Objects at a constant temperature emit infrared
would be absorbed by the lter radiation at the same rate as it absorbs it
• On the other hand, lters that aren’t primary • Some colours and surfaces absorb and emit
colours let the wavelengths of like for that colour radiation better than others. E.g. a black matt
through, as well as the primary colours that are surface is the best absorber and emitter, whereas
combined to make that speci c colour a shiny white surface is the worst
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