Jigglypuff gets a microphone
Jigglypuff, after realizing that the gum that Bob gave him was making him sing less loudly (see Jigglypuff 1 ), decides to get a microphone.
His microphone makes a sound of 120 dB at 1 meter, and any sound greater than 20 dB makes people fall asleep.
If Jigglypuff is currently in Goldenrod City, will Ash Ketchum in Pallet Town 84 km away fall asleep, and how loud will the sound be to him?
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1 solution
Moderator note:
Simple standard approach.
120 dB = 1 W/m^2 20 dB = 1 * 10^-10 W/m^2 Inverse square law: Square root of 10^10 is 10^5 So the range is 100 km which is bigger than 84 km so Ash Ketchum will fall asleep.
84000^2 / 100000^2 = 0.7056
1/0.7056 = 1.41
log 1.41 = 0.15
0.15 * 10 = 1.5
20 + 1.5 = 21.5 dB.