EXE$\mathrm{.}1$A$.$SL$.$TZ$0.5$

Window $1$ is made of a single glass pane of thickness $d.$ Window $2$ is made of two glass panes

of thickness $d$ each, separated by a thin air space. Both windows have the same surface area

and separate air masses of the same temperature difference.

Thermal energy transferred in unit time through window $1$ is $Q.$ The thermal energy transferred in

unit time through window $2$ is

A$.$ less than $\frac{Q}{2}$

B$.$ equal to $\frac{Q}{2}$

C$.$ between $\frac{Q}{2}$ and $Q$

D$.$ equal to $2Q$

Please provided a detailed explanation of the answer.

Thank you!