Correct option is E
The transparent cover (usually made of glass or plastic) in a flat-plate solar collector serves multiple important functions:
To reduce energy loss: It prevents convective and radiative heat loss from the absorber plate to the surroundings.
To transmit visible light: It allows solar radiation (shortwave), especially visible and near-infrared light, to pass through and reach the absorber plate.
To block far-infrared rays: It blocks re-radiated longwave (far-infrared) thermal energy from escaping back, effectively trapping heat inside (greenhouse effect).
To ensure more incoming solar radiation energy: By optimizing angle and clarity, it helps maximize solar radiation capture by the absorber.
