Number of photons in decimals?

[Ice-cream]

with this question, I'm told that i shouldn't be getting any decimal answers becuase the answer is in the number of photons...so can any1 just tell me whether you agree with my answer?

 

A ruby laser produces radiation of wavelength 633nm in pulses of 1.00e-9 s duration. If the laser produces 1.68e-16J of energy per pulse, how many protons are produced in each pulse?

 

i keep getting an answer of 535.46827.... which i think is approx. 535 photons. what do you guys think?

[ed84c]

The results you have obtained are not accurate enough.

 

State that in your answer (if H/W) or do the test again (if an experiment).

[Ice-cream]

but the answer wants the number of photons...no matter how accurate my answer is, wouldn't it still round up to 535 photons anyway? (the problem is my lecturer said if the answer is wanting the "number" of photons, I shouldn't be getting a decimal answer).

[Meir Achuz]

Your difficulty is in significant figures. Since the input numbers are given to 3 sf,

your answer is only accurate to 3 sf. All the numbers after the decimal are meaningless. Your answer is 535 photons.

[ed84c]

Your difficulty is in significant figures. Since the input numbers are given to 3 sf' date='

your answer is only accurate to 3 sf. All the numbers after the decimal are meaningless. Your answer is 535 photons.[/quote']

 

Yeh, when i said results, I meant results of the experiment given to you, not your answer.

[Ice-cream]

ahh, i c, what about the answer itself? do you agree with 535? (i used E = hc/wavelength) (i'm not sure if the time was necessary in the calculations but i found i didn't need to use it...what do u guys say?)

[ed84c]

Im quite happy with that, but make sure you DO quote the problem in your answer, atleast then if we're incorrect, you still may get follow through marks/ help to where you went wrong.