Question

In my book its written black objects rradiate and absorb more heat than white objects. Thus the back of refrigerators is coloured dull black so that they can raiate maximum hat to cool down the refrigerator pipes.

BUT BLACK COLOUR OBJECTS ABSORB MORE HEAT TOO. THEN REFRIGERATORS WILL HEAT UP. ISNT IT?

Answer 1

Yes you are right. But any object can not heat up all by itself. There should be source of heating. There is no source to heat up the piper externally. Roughly speaking, it gets heat up by the taking away the heat from the food inside the refrigerator. And that happens from the inside of the pipe. Once it gets the heat now it should radiate it to cool down. That is why it is made black to cool it down fast by radiating the heat. So you can assume it as a black object heating up from inside and radiating. But there is no source of heat to heat it up from outside.