Create the radiation-heat transfer rates

Question

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Q: Consider two large (infinite) parallel planes that are diffuse-gray with temperatures and emissivities of T1, e1 and T2, e2. Show that the ratio of the radiation transfer rate with multiple shields, N, of emissivity es to that with no shields, N = 0 is, where q12, N and q12, O represent the radiation heat transfer rates for N shields and no shields, respectively.

q_12,N/q_12,0 - [1/ε₁+1/ε₂-1]/ +[1/ε₁+1/ε₂-1]+N[2ε₂-1]