<P> Refraction is the change in direction of wave propagation due to a change in its transmission medium . </P> <P> The phenomenon is explained by the conservation of energy and the conservation of momentum . Owing to the change of medium, the phase velocity of the wave is changed but its frequency remains constant . This is most commonly observed when a wave passes from one medium to another at any angle other than 0 ° from the normal . Refraction of light is the most commonly observed phenomenon, but any type of wave can refract when it interacts with a medium, for example when sound waves pass from one medium into another or when water waves move into water of a different depth . Refraction follows Snell's law, which states that, for a given pair of media and a wave with a single frequency, the ratio of the sines of the angle of incidence θ and angle of refraction θ is equivalent to the ratio of phase velocities (v / v) in the two media, or equivalently, to relative indices of refraction (n / n) of the two media . Epsilon (ε (\ displaystyle \ epsilon)) and mu (μ (\ displaystyle \ mu)) represent the dielectric constant and the magnetic moment of the different media: </P> <Dl> <Dd> sin ⁡ θ 1 sin ⁡ θ 2 = v 1 v 2 = n 2 n 1 = (ε 2 μ 2 ε 1 μ 1) (\ displaystyle (\ frac (\ sin \ theta _ (1)) (\ sin \ theta _ (2))) = (\ frac (v_ (1)) (v_ (2))) = (\ frac (n_ (2)) (n_ (1))) = (\ sqrt (\ left ((\ frac (\ epsilon _ (2) \ mu _ (2)) (\ epsilon _ (1) \ mu _ (1))) \ right)))) </Dd> </Dl>

8. what is a refracted wave give an example
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