A normal lens has pincushion distortion or barrel distortion which can be corrected to give a perfect perspective projection, like the image of a pin-hole camera.
This process is called “rectification” and is often applied for stitchich images, for example, in panoramic photography.
The resulting images has no distortion.
With , roughly 300000km per second
In other media than vacuum the light
is slower. Therefore, the smallest refraction
index is 1.
The speed of light in the medium is
Therefore the speed of light in a medium is factor “refractive Index” slower than the speed of light c in vacuum.
Glass slows down light of different wavelengths (“colors”) by different factors.
Results are different refractive indices, “depending on the color (wavelength) of light .”
The higher the refraction index, the stronger the change of direction at the boundary between different media
As media have different refraction index for blue, green red light, red/green/blue light takes a different path through a lens
||typical refractive index
|Water at 20 °C
|Ethanol at 20 °C
|Olive oil at 20 °C
|PMMA (= acrylic = plexiglas)
|Flint glass (typical)
After a reflection light propagates from right to left, and it’s velocity can be regarded as negative. Using velocity instead of speed in the above equation, the index of refraction can also be regarded as negative.