For a good conductor, the depth of penetration of electromagnetic wave is given by:

• A. \(\delta = {\left[ {\frac{2}{{\omega \sigma \mu }}} \right]^{\frac{1}{2}}}\)
• B. \(\delta = {\left[ {\frac{1}{{\omega \sigma \mu }}} \right]^{\frac{1}{2}}}\)
• C. \(\delta = {\left[ {\frac{2}{{\omega \sigma^2 \mu }}} \right]^{\frac{1}{2}}}\)
• D. \(\delta = {\left[ {\frac{2}{{\omega \sigma }}} \right]^{\frac{1}{2}}}\)