If ε is the emissivity of surfaces and shields and n is the number of shields, introduced between the two surfaces, then overall emissivity is given by

• A. \(\frac{1}{{n \epsilon}}\)
• B. \(\frac{1}{{n\left( {2 - \varepsilon } \right)}}\)
• C. \(\frac{1}{{\left( {n + 1} \right)\left( {2 - \varepsilon } \right)}}\)
• D. \(\frac{\varepsilon }{{\left( {n + 1} \right)\left( {2 - \varepsilon } \right)}}\)