Question

ReviewI ConstantsI Periodic Table Use the inverse square law for light to answer each of the following questions Part C Suppose a star has a luminosity of 6.0x1028 watts and an apparent brightness of 2.0x10-12 watt/m2. How far away is i? Give your answer in both kilometers and light-years Express your answer using two significant figures km Submit Part D Express your answer using two significant figures d- light - years Submit Request Answer

Answer 1

We know that the brightness is given by
$B = \frac{L}{4\pi D^{2}}$
Where B is brightness
L is luminosity
D is distance
Now on putting the values
$2*10^{-12} = \frac{6*10^{26}}{4\pi d^{2}}$
d = 4.89*10¹⁸ m
We know that
1 km = 1000 m , therefore
d = 4.89*10¹⁵ km
Now we know that
1 light year = 9.461*10¹² km
d = 4.89*10¹⁵*(1/9.461*10¹² ) = 516.44 light years