If two metallic plates of equal thickness and thermal conductivities `K_(1)` and `K_(2)` are put together face to face and a common plate is constructed, then the equivalent thermal conductivity of this plate will be

Options

A. `(K_(1)K_(2))/(K_(1)+K_(2))`
B. `(2K_(1)K_(2))/(K_(1)+K_(2))`
C. `((K_(1)^(2)+K_(2)^(2))^(3//2))/(K_(1)K_(2))`
D. `((K_(1)^(2)+K_(2)^(2))^(3//2))/(2K_(1)K_(2))`

Answer

B