Problem

1. When describing stars, state what is meant by the term apparent brightness,

b

? 2. i Show that the apparent brightness,

b_{\odot}

, of our Sun, of luminosity

L_{\odot} = 3.83 \times 10^{26}

W, is

b_{\odot} = 1.4 \times 10^3

Wm^-2. The Sun is

1.5 \times 10^{11}

m away from the Earth. ii By what name is this quantity usually known? 3. Calculate the apparent brightness of a star that has a luminosity of

5.0 \times 10^{28}

W if it is four light-years away.