Question

Question #02d1f

Answer 1

`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`