A wall consists of alternating blocks withlength 'd' and coefficient of thermal conductivity `k_(1)` and `k_(2)`. The cross sectional area of the blocks are the same. The equivalent coefficient of thermal conductivity of the wall between left and right is:-

Explanation

`Q_(1)=(lambda_(2))/(d)(T_(1)-T_(0))A` and `Q_(2)=(lambda_(2))/(d)(T_(1)-T_(0))A`
`Q=Q_(1)+Q_(2)`
`lambda=((lambda_(1)+lambda_(2))/(2))`