Find the distance to a Sun-like star (L=3.8x1026 watts) whose apparent brightness at Earth is 1.0 x10-10 watt/m2.

Respuesta :

Answer:

5.49 x 10^17 m  is the distance between the sun-like star to the earth

Explanation:

Radiation intensity on Earth = 1.0 x 10^-10 W/m^2

Power of radiation of the star = 3.8 x 10^26 W

Recall that the intensity of radiation is given as

[tex]I[/tex] = [tex]\frac{P}{A}[/tex]

where

[tex]I[/tex] = intensity of radiation

P = power of radiation

A is the area through which the radiation spreads out in all three dimensional direction.

A = [tex]\frac{P}{I}[/tex] = [tex]\frac{3.8*10^{26} }{1.0*10^{-10} }[/tex] = 3.8 x 10^36 m^2

This area is spread out in the form of a sphere of area

A = [tex]4\pi r^{2}[/tex] = 4 x 3.142 x [tex]r^{2}[/tex]

3.8 x 10^36 = 12.568[tex]r^{2}[/tex]

[tex]r^{2}[/tex] =  (3.8 x 10^36)/12.568 = 3.02 x 10^35

r = [tex]\sqrt{3.02*10^{35} }[/tex] = 5.49 x 10^17 m   this is the distance of the star to the Earth

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