Topic 7 - Light and lenses Flashcards
What is the visible light spectrum ?
A tiny part of the EM spectrum that is visible to the human eye.
Each colour corresponds to a wavelength/frequency range
mnuemonic for remembering order of colours ( longest - shortest wavelengths )
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Specular reflection
when parallel waves are reflected in the same single direction by a smooth surface
diffuse reflection
when parallel waves are reflected in lots of different directions, scattered by a rough surface
transparent objects
- transmits light in straight lines so you can clearly see an image through it
translucent objects
- transmits light but scatters it so you can see clearly through them
obaque objects
- don’t transmit light at all but just absorb and reflect
how is the colour of an obaque object determined
- which wavelengths of light are most strongly reflected ( the rest of wavelengths are absorbed )
why do obaque objects appear white?
because they reflect all wavelengths of light equally
why do obaque objects appear black?
because they don’t reflect any light and absorb all wavelngths of light
what are colour filters?
only transmits certain wavelengths of colours and absorbs the rest
objects & infrared radiation
-all objects emit and absorb IR.
- the hotter the object is the more IR the object emits
surroundings & infrared radiation
- if an object is hotter than its surroundings than it will emit more IR than it absorbs, and so its temperature falls
- vice versa
- if an object is at a constant temperature it wil emit/absorb IR at same rate
What is a perfect black body?
A black body absorbs all EM radiation and is the best possible emitter
when the temperature of an object increases
- intensity of every wavelength increases
- peak wavelength decreases
