Step-by-step explanation:
- Length of rectangle = 7 less than the twice the breadth
- Perimeter = 40 cm
Let us say the breadth as b and length as l.
→ Length = 7 less than the twice the breadth
→ l = 2b - 7 ...(1)
Now, according to the question,
→ Perimeter of rectangle = 2(l + b)
→ 40 = 2(2b - 7 + b)
→ 40 = 2(3b - 7)
→ 40 = 6b - 14
→ 40 + 14 = 6b
→ 54 = 6b
→ 54 ÷ 6 = b
→ <u>9</u><u> m = Breadth</u>
Now, finding length.
→ l = 2b - 7
→ l = 2(9) - 7 m
→ l = 18 - 7 m
→ <u>Length = 1</u><u>1</u><u> m</u>
Sound intensity corresponding to 80 dB: ![1\cdot 10^{-4}W/m^2](https://tex.z-dn.net/?f=1%5Ccdot%2010%5E%7B-4%7DW%2Fm%5E2)
Step-by-step explanation:
The decibel of a normal conversation is 60 dB, which corresponds to an intensity of
. (1)
The formula to use that relates the intensity of the sound in
to the sound level in decibel is
![\beta(dB)=10log_{10}(\frac{I}{I_0})](https://tex.z-dn.net/?f=%5Cbeta%28dB%29%3D10log_%7B10%7D%28%5Cfrac%7BI%7D%7BI_0%7D%29)
Where
is the sound level in decibel
is the intensity
We can found
by plugging in the numbers of (1):
![\frac{\beta(dB)}{10}=log_{10}(\frac{I}{I_0})\\\frac{I}{I_0}=10^{\frac{\beta(dB)}{10}}\\I_0 = \frac{I}{10^{\frac{\beta(dB)}{10}}}=\frac{1\cdot 10^{-6} W/m^2}{10^{\frac{60}{10}}}=1\cdot 10^{-12} W/m^2](https://tex.z-dn.net/?f=%5Cfrac%7B%5Cbeta%28dB%29%7D%7B10%7D%3Dlog_%7B10%7D%28%5Cfrac%7BI%7D%7BI_0%7D%29%5C%5C%5Cfrac%7BI%7D%7BI_0%7D%3D10%5E%7B%5Cfrac%7B%5Cbeta%28dB%29%7D%7B10%7D%7D%5C%5CI_0%20%3D%20%5Cfrac%7BI%7D%7B10%5E%7B%5Cfrac%7B%5Cbeta%28dB%29%7D%7B10%7D%7D%7D%3D%5Cfrac%7B1%5Ccdot%2010%5E%7B-6%7D%20W%2Fm%5E2%7D%7B10%5E%7B%5Cfrac%7B60%7D%7B10%7D%7D%7D%3D1%5Ccdot%2010%5E%7B-12%7D%20W%2Fm%5E2)
Which corresponds to a sound level of 0 decibel.
Now we can find the intensity that corresponds to a sound level of
![\beta=80 dB](https://tex.z-dn.net/?f=%5Cbeta%3D80%20dB)
And from the equation we find:
![I=I_0 10^{\frac{\beta(dB)}{10}}=(1\cdot 10^{-12})10^{\frac{80}{10}}=1\cdot 10^{-4}W/m^2](https://tex.z-dn.net/?f=I%3DI_0%2010%5E%7B%5Cfrac%7B%5Cbeta%28dB%29%7D%7B10%7D%7D%3D%281%5Ccdot%2010%5E%7B-12%7D%2910%5E%7B%5Cfrac%7B80%7D%7B10%7D%7D%3D1%5Ccdot%2010%5E%7B-4%7DW%2Fm%5E2)
Learn more about sound waves:
brainly.com/question/4899681
#LearnwithBrainly
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