A progressive wave carries energy and information without transferring material
Waves carry energy- electromagnetic waves heat, x-rays and gamma rays ionise, sounds makes things vibrate, wave power can generate electricity and wave sources lose energy (as give it to the waves)
Reflection- a wave is bounced back when hits a boundary
Refraction- the wave changes direction when it enters a different medium
Frequency= 1/period
Speed of wave= wavelength x frequency
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Forming Images With Lenses
When light meets a boundary of mediums, some is reflected back into the 1st medium and the rest is transmitted
The more optically dense a material is, the more slowly light travels in it
Absolute refractive index= speed of light in a vacuum/ speed of light in material
Lenses change the curvature of wavefronts via refraction
A lens adds curvature- they slow down the light travelling through the middle for a longer time than for the edges
Focal length (f) is the distance between the lens axis and the focus
More powerful the lens- more strongly will curve the wave- shorter focal length
Power (dioptres)= 1/ focal length
Curvature= 1/radius of curvature
The linear magnification of a lens (m)= size of image/ size of object
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Information in Images
The binary system uses two digits, 1 and 0
A single binary digit is a bit, and 8 bits make up a byte
The number of bits in a string of info determines how many alternatives the string can code for
Each pixel in an image is represented by a binary number
The value of the binary number gives the colour (or shade of gray) of the pixel
In coloured images, each pixel is described by three binary numbers (one for each primary colour- red, blue and green)
Addition of false colour is used to highlight certain, important features
Noise is unwanted interference affecting a signal
Noise can be removed by replacing each pixel with the median of itself and the 8 pixels surrounding it
Any odd values are removed and the image is smoother
Finding edges is useful when working out if there is something useful in the image (not just noise)
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