In astronomical observations, signals observed from the distant stars are generally weak





Q.48:- In astronomical observations, signals observed from the distant stars are generally weak. If the photon detector receives a total of 3.15×10-18 J from the radiations of 600 nm, calculate the number of photons received by the detector.

 

 

Answer:-
Energy of one photon = hν = hc/λ = (6.626×10-34 Js×3.0×10ms-1)/600×10-9 m = 3.313×10-19 J
Total energy received = 3.15×10-18 J
∴ No. of photons received = 3.15×10-18 J/3.313×10-19 J = 9.51 (approx 10)