Caption: A diagram illustrating the dispersion of a light ray by a prism and plate glass.
Features:
n_1*sin(θ_1) = n_2*sin(θ_2) ,where the n_i are the refractive indexes n = c/v_i (where c is the vacuum light speed c = 2.99792458*10**8 m/s and v_i is the light speed in medium i: c ≥ v_i) and the θ_i are the angles of light ray from the normal (i.e., the perpendicular) to the medium interface.
Note
sin(θ_2) = (n_1/n_2)*sin(θ_1) ,and so θ_2 subceeds/exceeds θ_1 if n_2 is greater/lesser than n_1.
Most common transparent solids and liquids have n_i greater than n_air, and so light rays bend toward/away the normal when entering/leaving these common materials.
Note the oblique medium interfaces cause the dispersion to increasing going through the second medium interface rather than cancel.
Thus, dispersion creates a spectrum.
So any dispersion from oblique incidence is canceled by a remixing of the colors.
Note the diagram is WRONG in showing refraction for light rays incident along the normal. Light rays incident along the normal do NOT refract.
Credit/Permission: ©
David Jeffery,
2003 / Own work.
Image link: Itself.
Local file: local link: refraction_prism.html.
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refraction_prism.html.