# Search results

1. ### De Broglie wavelength of electron and proton

Thanks @ehild , @Phylosopher , @Charles Link for your valuable inputs :smile:
2. ### Heat radiation and photons

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...
3. ### De Broglie wavelength of electron and proton

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...
4. ### Heat radiation and photons

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

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

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 .
7. ### Heat radiation and photons

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...
8. ### Heat radiation and photons

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 ?
9. ### Heat radiation and photons

Assuming the question is considering time after the hot body is placed , do you think my reasoning is correct ?
10. ### Heat radiation and photons

Homework Statement Homework Equations The 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 !
12. ### MCQ : Comparing characteristics of two photons

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 ) .
13. ### MCQ : Comparing characteristics of two photons

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 ?
14. ### De Broglie wavelength of electron and proton

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 .
15. ### MCQ : Comparing characteristics of two photons

I think d) will be correct .
16. ### De Broglie wavelength of electron and proton

Could you show me how you get this result . What is rest energy ?
17. ### De Broglie wavelength of electron and proton

I have . But I thought this was obtained from the formula E2 = P2c2 + m02c4 by putting P = 0 . I thought E = mc2 was valid for a particle at rest i.e for a particle having zero momentum .
18. ### De Broglie wavelength of electron and proton

How did you get E=mc2 ? What is γ ?
19. ### MCQ : Comparing characteristics of two photons

Homework Statement Homework Equations The Attempt at a Solution I am surely making some very silly mistake in this problem . Presuming linear momenta means magnitude of momentum , to me all four options look correct . a) since wavelengths are same , energy is same which means momentum...
20. ### De Broglie wavelength of electron and proton

Homework Statement Homework Equations The Attempt at a Solution de Broglie wavelength λ of a particle = h /P a) since mass of proton is more than electron and speed is same , momentum of proton is more . De Broglie wavelength of proton will be less . b) wavelengths will be same . c)...

Thanks !
22. ### Is this question on Intensity of light from Sun correct?

Homework Statement Homework Equations The Attempt at a Solution This is an example given in the book . But I am just wondering whether the question itself is correct . How can intensity of light emitted from Sun is given a constant ? Shouldn't 1400 be the power emitted from Sun ? If...

Thanks !
24. ### Comparing self inductance of three solenoids

Thanks all for your precious inputs .
25. ### Magnetic field and coplanar loops

While applying Faraday in the outer loop , what area should I use , area of the outer loop OR area of the outer loop minus area of the inner loop ? @Charles Link , @cnh1995
26. ### Comparing self inductance of three solenoids

Hi cnh1995 , Interesting ! You showed L = 0 and then chose option a) Did you mean option c) :smile: ? What is the mistake in the reasoning in latter part of post#26 ?
27. ### Comparing self inductance of three solenoids

Please refer to post#22 . How ? Is it because windings are reversed in each layer such that if first winding is CW , next is ACW , then CW , such that flux from any two neighbouring turns cancel each other . The net flux for the complete solenoid being zero , making L2 = 0 ?
28. ### Comparing self inductance of three solenoids

Glad that we all agree :smile:
29. ### LR circuit - Which bulb gets dim quickly?

B1 would get brighter but B2 would remain same for a moment .Then both get dimmer .Right ?

Why ?