Question

The luminosity of the Sun is 4*10^33 erg/s, and its radius is 7*10^10 cm.
What is the flux of sunlight on the Earth?

Answer 1

1 erg/s = 10^(-7) watt
So, The luminosity of the Sun becoms now
=4x[10^33] x 10^(-7) watt
=4x [10^26] watt

Radius
=7x10^10cm
=7x10^5km

Surface area
=4πr²
$=4* \frac{22}{7} * [7* 10^{5}] ^{2}$
$=616* 10^{10} km^{2}$

We know, that
$Flux=\frac{Power}{Surface area}$
$Flux= \frac{4* 10^{26} }{616* 10^{10} }$
$Flux= 6.49* 10^{13} watt/ km^{2}$

Answer 2

heya...

here is your answer...

1 Watt = 1 J/s = 10^7 erg/s

1GW = 10^9 J/s

the area of the sun is

4pi*(7*10^5 km)^2 = 6.2*10^12 km^2

So the solar output is

4*10^17 GW/6.2*10^12km^2

= 6.452*10^4 GW/km^2

it may help you...