Question

The density and atomic no. of niobium are 8.57 x 10 kg/m³ and 93, respectively. It has one conduction electron per atom. Calculate the London penetration depth of niobium.

Answer 1

$$\lambda=\sqrt\frac{m_e}{\mu_0ne^2},\\\space\\ \lambda=\sqrt\frac{m_eM}{\mu_0N_A\rho e^2}=22.6\text{ nm}.$$

M above is the molar mass, 0.093 kg/mol, m_e is the mass of electron, e is the elementary charge.