I believe that it is the first one just a guess tho. So don't trust me, just in case
Answer:
3.066×10^21 photons/(s.m^2)
Explanation:
The power per area is:
Power/A = (# of photons /t /A)×(energy / photon)
E/photons = h×c/(λ)
photons /t /A = (Power/A)×λ /(h×c)
photons /t /A = (P/A)×λ/(hc)
photons /t /A = (680)×(678×10^-9)/(6.63×10^-34)×(3×10^-8)
= 3.066×10^21
Therefore, the number of photons per second per square meter 3.066×10^21 photons/(s.m^2).
NOTE: The strength of an electromagnet is directly proportional to not only the current but the number of windings. Doubling the number of windings doubles the strength of the magnet.
I think the answer is A because it’s a better explanation
