Question #02d1f

1 Answer
Apr 20, 2017

Answer:

#4.948xx10^-4J#

Explanation:

As answered for your other question
A sound level of #90.0 dB# converted in units #Wm^-2# is

Let #90.0dB=xWm^-2#

Implies that
#10 log(x/(1xx10^-12))=90#
#=> log(x/(1xx10^-12))=9.0#
Taking #"anti "log#
#=> x/(1xx10^-12)=10^9#
#=> x=10^9xx1xx10^-12#
#=> x=10^-3Wm^-2#

Energy falling on eardrum #="Intensity"xx"Area"#
#=10^-3xxpi(0.500/2xx1/100)^2 #
#=1.9634xx10^-8W#

Total energy falling on the ear drum in #7#hours
#=1.9634xx10^-8xx7xx3600#
#=4.948xx10^-4Wcdot s#

Since joule is also watt-second, therefore
Total energy falling on the ear drum in #7#hours#=4.948xx10^-4J#