PHYSICS HELP PLEASE?

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  • oubaas
    Lv 7
    1 month ago

    If you are d = 35 m far : 

    Sphere outer area A = PI*70^2 = 4900Pi m^2

    I = P/A = 7/(4900PI) = 4.547*10^-4 watt/m^2I(dB) = 10Log (4.547*10^-4*10^12) = 86.58 dB

    If you are just d' =10 m far : 

    Sphere outer area A' = PI*20^2 = 400Pi m^2

    I' = P/A' = 7/(400PI) = 5.570*10^-3 watt/m^2

    I'(dB) = 10Log (5.570*10^-3*10^12) = 97.46 dB

    if you want to hear I'' = 18*I' , your distance d'' would be d'/√ 18 = 10/√ 18 = 2.357 m

    check :

    Sphere outer area A'' = PI*4.714^2 = 22.22Pi m^2

    I'' = P/A'' = 7/(22.22PI) = 0.100 watt/m^2

    5.570*10^-3*18 = 0.100 watt/m^2 ....it works !!!

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