The magnetic induction in vacumm at a plane surface of a uniform istropic magnetic is equal to `B`, the vector `B` forming an angle `alpha` with the normal of the surface. The permeability of th emagnetic is equal to `mu`. Find the magnitic of the magnetic induction `B"` in the magnetic in the vicinity of its surface.

Explanation

`B'_(n) = B cos alpha`,
`H'_(t) = (1)/(mu_(0)) B sin alpha`,
`B' = mu B sin alpha`
so,
`B' = B sqrt(mu^(2) sin^(2) alpha + cos^(2) alpha)`