有關log的應用題----音量的強度

The equation which relates the intensity of a sound wave to its decibel level is:

dB = 10 * log( I / 1 x 10^-12 W/m^2)

(http://www.glenbrook.k12.il.us/gbssci/Phys/chemphys/reviews/u4review/u4ans3.html)

即係呢...

103 = 10 * log( I / 1 x 10^-12)
103 = 10 * [log I - log (1 x 10^-12)]
103/10 = log I - log (1 x 10^-12)
10.3 = log I - (-12)
10.3 = log I + 12
log I = 10.3 -12
log I = -1.7
I = 0.01995 W/m^2 (0.020, 3 sig. fig.)

我諗應該 o岩 ga.....
呢個 website 話 100dB 即係 1*10^-2 W/m2 (0.01 W/m^2)
http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/u11l2b.html

希望幫到你 =]