# Homework Help: What is granularity?

1. Jan 15, 2005

### Athalus

I don't know what they mean in my assignment refering to granularity in question 3)e) of the assignment found below.

3) [5 marks] A radio station broadcasts at a frequency of 2MHz with a total radiated power of 1000W.
a. What is the wavelength of this radiation?
b. What is the energy of the individual quanta that compose the radiation?
c. How many photons are emitted per second?
d. A certain radio receiver must have 5 microwatts of radiation incident on its antenna in order to provide intelligible reception. How many photons per second are required?
e. In view of your answers to (c) and (d), can granularity of electromagnetic radiation in these circumstances be neglected?

I think it means the integrity of the signal, which i believe is good since the ratio of delivered power to that of the minimum required power is very high in the order of 10^8

Thanks for any clarification
Athalus

2. Jan 16, 2005

### dextercioby

To answer your question from the title,i would say "granular=corpuscular" in this case "photonic"...Did u compute the number of photons??

Daniel.

3. Jan 16, 2005

### Athalus

Yes I did compute the number of photons emitted per second in part c, approximately something in the order of 10^29 photons per second, and I calculated the minimum number of photons required in part d, approximately something in the order of 10^21 photons per second, I'm just wondering what they mean by granularity, which I think means is there sufficient photons so that granularity of the signal is not an issue, which I believe there is.

Thanks
Athalus

4. Jan 16, 2005

### dextercioby

I don't feel like checking your numbers,they seem correct.If in the second case,the one with a small intensity,the nuber of photons is still big (10^{21}/s),then the "granularity" can be neglected,because the quantum effects,the ones which include the word "photon",are valid only when the nummer of particles is really small...The number you've got is HUGE...

Daniel.

5. Jan 16, 2005

### Athalus

Thanks, but I still don't quite understand what your telling me, is it that granularity refers to what happens when there are quantum effects involved, and that I can disregard it because the number of photons is so large that quantum effects do not come into play?

Thanks Again,
Athalus

6. Jan 16, 2005

### dextercioby

Yes,"granularity" of light is definitely a quantum effect.

Ã‰xactement,that's the explanation...You got the idea...Congratulations...

Daniel.

7. Jan 16, 2005

### Athalus

But the question is not refering to the granularity of light, the question is refering to the "...granularity of electromagnetic radation...", or radio waves I believe, I don't know if it really matters though, it probably is the same thing as the granularity of light.

Thanks,
Athalus

8. Jan 16, 2005

### dextercioby

Okay,light is em.radiation.It's just that it's in the visible spectrum.There are radio photons as well,just like gamma,X,visible...

Daniel.