Light travels through air faster than it travels through water. How would the light refract differently if the keys were in air, and the boy was looking
at them from underwater?

The fastest thing in the whole universe is the speed of light in a vacuum (like outer space!), clocking in at a great 2.99 x 108 m/s. Light travels in waves, and we call this traveling propagation. Propagation of waves has both a speed and a direction, called the velocity. The velocity of light changes depends on the material it travels through.

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waves moving from a fast medium to a slow medium will experience a reflection as light travels more slowly than red light. total internal reflection occurs when the critical angle is.

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