what combination of mediums will produce a stright line of light?

how do you correct for hyperopia?
how do you correct for myopia?
what kind of people have an astigmatism?
what part of the eye act as a lens and what part acts as a screen?
how do different types of lenes bend light?
what could you do to get a shorter focal length?
how do you get the shortest focal length using tweo lenses?
what is the angle of incidence?
what is the angle of refraction?
what is the angle of emergence?
what is the name for bending light?
how does light travel? always?
how does light travel through different mediums?
what happens to an image once it goes through a lens?
how did the greeks think humans could see?

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