The of a wave is the bending of a wave as it passes through one medium to another medium.

Refraction is the change of direction and speed that a wave experiences when passing from one medium to another with different refractive index. It only occurs if the wave strikes obliquely on the separation surface of the two media and if they have different refractive indices. The refraction originates in the change of velocity of propagation of the indicated wave.

this statement is true.

forests are public goods, available for everybody. when usage of such a good becomes interesting for consumers and its usage increases, there can be a risk of overexploitation. it is a non rival good therefore, if one person consumes the good it does not reduce the availability for subsequent consumers.

these caracteristics require the establishment of measures in order to prevent the destruction of a commonly owned space, for example, to restrict the amount of people that have access to the same time.