(a) the intensity of sound coming from a speaker 2 m away is 80 db. how far away must you stand for the intensity to be reduced to 40 db? (b) the earth has a radius of r = 6.4 106 m. it orbits the sun in a nearly circular orbit at an average distance of 1.5 101m. the solar intensity at the upper atmosphere is 1367 w/m2. how much energy does the sun radiate per second?

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Ответ:

mgreer432

21.07.2020

Physics

$3.031\times 10^{-5}\ \text{m}$

Explanation:

= Distance between central maxima and first minimum

m = Order = 1

d = Thickness of hair

$\lambda$ = Wavelength = 632.8 nm

L = Distance between light source and screen = 1.25 m

Width of central maximum is given by

$2y=5.22\times 10^{-2}\\\Rightarrow y=\dfrac{5.22\times 10^{-2}}{2}\\\Rightarrow y=0.0261\ \text{m}$

Distance between central maxima and first minimum is given by

$y=L\tan\theta_{min}\\\Rightarrow \tan\theta_{min}=\dfrac{y}{L}\\\Rightarrow \tan\theta_{min}=\dfrac{0.0261}{1.25}\\\Rightarrow \theta_{min}=\tan^{-1}0.02088\\\Rightarrow \theta_{min}=1.1962^{\circ}$

Since $\theta$ is small $\tan\theta_{min}=\sin\theta_{min}$

$\sin\theta_{min}=\dfrac{m\lambda}{d}\\\Rightarrow d=\dfrac{m\lambda}{\sin\theta}\\\Rightarrow d=\dfrac{1\times 632.8\times 10^{-9}}{\sin1.1962^{\circ}}\\\Rightarrow d=3.031\times 10^{-5}\ \text{m}$

The strand of hair is $3.031\times 10^{-5}\ \text{m}$ thick.

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