Out of two solar cookers, one was covered by a plane glass slab and the other was left open. Which of the two solar cookers will be more efficient and why ?

Explanation

The solar cooker covered by plane glass slab will be more efficient than the one which is left open. This is due to the reason that the plane glass slab enables the cooker to trap heat inside it. On this account, the temperature inside the cooker rises. In fact, the plane glass slab placed on the cooker produces a kind of greenhouse effect.