1. Review of Stefan-Boltzmann Law and Practice Problems
The Stefan-Boltzmann Law relates the luminosity of a star to its surface area and temperature. It states that the luminosity of a star is a function of both its radius and its surface temperature. The relation is
where L is the stars luminosity, R is the star’s radius, σ is the Stefan-Boltzmann constant and T is the star’s temperature in Kelvins.

2. The working equation for Stefan-Boltzmann Law problems is
Practice Problem 1: If a star has twice the temperature of the Sun and half the radius of the Sun, what is its luminosity compared to the Sun’s?
Solution: Create the ratio of the S-B Law of the star with that of the Sun
Answer in a sentence: The star is four times more luminous than the Sun.

3. The working equation for Stefan-Boltzmann Law problems is
Practice Problem 2: If a star has a temperature of the 4,500 K and 100 times the radius of the Sun, what is its luminosity compared to the Sun’s?
Solution: Create the ratio of the S-B Law of the star with that of the Sun
Answer in a sentence: The star’s luminosity is 3,623 times that of the Sun.

4. The working equation for Stefan-Boltzmann Law problems is
Practice Problem 3: If a star has a temperature of the 25,000 K and 10,000 times the luminosity of the Sun, what is its radius compared to the Sun’s?
Solution: Create the ratio of the S-B Law of the star with that of the Sun
Answer in a sentence: The star’s radius is 5.38 times that of the Sun.

5. The working equation for Stefan-Boltzmann Law problems is
Practice Problem 4: If a star has a radius of the 2,000 times that of the Sun and is 100,000times the luminosity of the Sun, what is its temperature compared to the Sun’s?
Solution: Create the ratio of the S-B Law of the star with that of the Sun
Answer in a sentence: The star’s temperature is about that of the Sun’s temperature or about 40% of the Sun’s temperature.