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when a light ray passes from one medium to another at an angle
Refraction.
refraction
it changes in velocity
the light bends
If by "straight on" you mean at 90 degrees to the surface of the medium, that is because light is only deviated if it makes an angle with the normal, which is an imaginary line perpendicular to the surface of the medium. If no angle is made between the normal line and the light ray, then no refraction occurs and the light passes through in a straight line. For more information see the related link below.
it refracts
when a light ray passes from one medium to another at an angle
Refraction.
refraction
refraction
it changes in velocity
Refraction
the light bends
refraction
energy is independent of medium it passes through?
Refraction.