Two plates each of area A, thicknesses L1 and L2 and thermal conductivities K1 and K2 are joined to form a single plate of thickness (L1 + L2). If the temperatures of the free surfaces are T1 and T2, Find the temperature of interface:

Question

(A) [T1L2/K2 + T2L1/K1] / [L1/K1 - L2/K2]

(B) [T1L2/K2 + T2L1/K1] / [L1/K1 + L2/K2]

(C) [T1L1/K1 + T2L2/K2] / [L1/K1 + L2/K2]

(D)[T1L1/K1 - T2L2/K2] / [L1/K1 + L2/K2]