Recent content by Jahnavi

Thanks @ehild , @Phylosopher , @Charles Link for your valuable inputs :smile:

I think the same . Why ? Irrespective of the heat capacity of the hot object , it will start cooling down till it's temperature becomes equal to the room temperature . Rate of Heat transfer is proportional to the temperature difference (fourth power) . It will be maximum initially and...

In the OP in part c) I have assumed energy to be kinetic energy in which case the momentum of proton was more and wavelength smaller . But if I consider energy to be relativistic energy in part c) , then momentum of photon comes out to be less and wavelength of proton is longer . I hope you...

Exactly :smile: I asked this because of BvU's objection to my interpretation in post#2 and post#4 .

So let it be :smile: If the body cools , the rate of heat transfer will decrease and subsequently the number of photons . No ?

Please confirm one thing . What is your interpretation of the problem statement ? Are you comparing 1) the time before and after the hot body is placed . OR 2) the time after the hot body is placed till thermal equilibrium is achieved .

Don't you think we just need to consider whether the rate of heat transfer decreases or not ? As the temperature of hot body decreases , rate of heat transfer decreases . As a consequence , the photons comprising the heat radiations should decrease with time . Please have a relook at the OP...

Could you explain why my assumption that time after the hot body is placed is incorrect . Don't you think wording of the question should have been " Has the number of photons increased ? " if the question wanted to compare the number before and after the hot body is placed ?

Assuming the question is considering time after the hot body is placed , do you think my reasoning is correct ?

Homework Statement Homework EquationsThe Attempt at a Solution No . The number of photons should decrease . As the rate of heat transfer decreases with time , the net electromagnetic radiation from the hot body to the surroundings decrease . Heat radiations are composed of photons ...

Thanks !

No :smile: I asked because E = Pc doesn't involve vectors whereas in the OP direction of momentum vector was to be considered while relating to wavelength (energy ) .

In the relation E = Pc for a photon, are both the terms on RHS (momentum and speed ) treated as vectors and is it that a dot product is taken so as to get the energy term E ?

Are the two expressions equivalent ? What should we put for P (momentum ) ? Should it be mv ? I am studying basics of photons , so I am quite hesitant to use mv for momentum for other particles as well .

I think d) will be correct .