The working of solar cooker:
When sunlight comes and hits the mirrors of the solar cooker, then the reflection of lights occurs due to the mirror. This reflected light hits the food, and food observes all the sunlight rays to heat itself.
This absorption of light rays helps to cook the food placed inside the solar cooker.
The sunlight rays act as radiation inside the solar cooker, and these radiations get hit up after getting reflected from all the surfaces of the mirrors.
In a DIY solar cooker, aluminum foil is used to increase the reflection of light in the cooker so that more radiations get trapped in the cooker and cook the food faster.
Hence, aluminum foils are used to increase the reflection of lights.