Transform Planck's formula for space spectral density `u_(omega)` or radiation form the variable `omega` to the variables `v` (linear frequency) and `lambda` (wavelength).

Explanation

We write
`u_(omega)d omega = overset~(u)_(v)dv` where `omega = 2pi v`
Then `overset~(u)_(v) = (2picancelh(2piv)^(3))/(pi^(2)c^(3)) (1)/(e^(2picancelhv//kT)-1) = (16pi^(2)cancelhv^(3))/(c^(3))(1)/(e^(2picancelhv//kT)-1)`
Also `-overset~(u)(lambda, T)d lambda = u_(omega)d omega` where `lambda = (2pic)/(omega)`,
`d omega =- (2pic)/(lambda^(2))d lambda`
`overset~(u)(lambda,T) = (2pic)/(lambda^(2))u((2pic)/(lambda),T)`
`= (2pic)/(lambda^(2))((2pic)/(lambda))^(3)(cancelh)/(pi^(2)c^(3)) (1)/(e^(2cancelhc//lambdakT)-1) = (16pi^(2)c cancelh)/(lambda^(5))(1)/(e^(1picancelhc//lambdakT)-1)`