Respuesta :
Answer:
The correct answer is option 'c': 30 AUs
Explanation:
For a spherical wave front emitted by sun with total energy 'E' the energy density over the surface when it is at a distance 'r' from the sun is given by
[tex]e=\frac{E}{4\pi r^{2}}[/tex]
This energy per unit area is sensed by observer as intensity of the sun.
Let the initial intensity of sun at a distance [tex]r_{1}[/tex] be [tex]e_{1}[/tex]
Thus if the sun becomes 900 times dimmer we have
[tex]e'=\frac{e_{1}}{900}\\\\\frac{E}{4\pi r_{2}^{2}}=\frac{1}{900}\times \frac{E}{4\pi r_{1}^{2}}\\\\\Rightarrow r_{2}^{2}={r_{1}^{2}}\times 900\\\\\therefore r_{2}={r_{1}}\times {30}[/tex]
Thus the distance increases 30 times.
