Posted by **JOHN** on Monday, April 9, 2012 at 1:05pm.

The sun is 1.5 1011 m from the earth.

(a) Over what surface area is solar radiation spread at this distance?

(b) What is the total power radiated by the sun? (The sun delivers energy to the surface of the earth at a rate of approximately 1400 W/m2.)

(c) Treating the sun as a body of emissivity 1, estimate its temperature. The sun's radius is 6.96 108 m.

K

- physics -
**Elena**, Monday, April 9, 2012 at 2:06pm
a. A = 4•π•r^2 = 4•π•(1.5•10^11)^2 = =9•π•10^22 m^2.

b. Power density is p =1400 W/m^2.

The total power is

P = p•A =1400 • 9•π•10^22 =

=3.96•10^26 W.

c. Stefan-Boltzmann Law

R = σ•T^4,

R =P/A1 = P/(4• π•r1^2), is the black body irradiance,

σ =5.67• 10^-8 W•m^-2•K^-4 is the Stefan-Boltzmann constant,

T =[P/(A1• σ)]^1/4 ={3.96•10^26/[4• π•(6.96• 10^8)^2]}^1/4 = 5800 K.

## Answer This Question

## Related Questions

- Physics - The temperature of the Sun’s surface (the so-called photosphere) is ...
- astrophysics - 1) Every second the Sun outputs 3.90* 10^26 Joules of energy. ...
- astrophysics - 1) Every second the Sun outputs 3.90* 10^26 Joules of energy. ...
- Physics - At the upper surface of the earth's atmosphere, the time-averaged ...
- Physics - At the upper surface of the earth's atmosphere, the time-averaged ...
- Physics to Elena - At the upper surface of the earth's atmosphere, the time-...
- math - Hi, Nearly all of the energy used on earth comes originally from the sun...
- physics - he sun radiates like a perfect blackbody with an emissivity of exactly...
- physics - The sun radiates like a perfect blackbody with an emissivity of ...
- Physics - The sun radiates like a perfect blackbody with an emissivity of ...

More Related Questions