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# Lesson Worksheet: Luminosity Physics

In this worksheet, we will practice calculating the flux density due to the energy radiated by a star at a given distance away from the star.

**Q1: **

The Sun has a luminosity of W. What is the flux density from the Sun at Neptune, a distance of 30.1 AU away from the Sun? Use a value of m for the length of 1 AU. Give your answer to two decimal places.

**Q2: **

Star A has a luminosity and star has a luminosity . At a distance away from star and a distance away from star , the flux densities due to each star are equal. What is the ratio ?

- A1
- B2
- C
- D4
- E

**Q3: **

The Peony star, which is located near the galactic center, has a luminosity of . At what distance from this star is the flux density equal to the flux density from the Sun at Earth? Use a value of m for the length of 1 AU and W for the luminosity of the Sun. Give your answer in scientific notation to two decimal places in astronomical units.

- A AU
- B AU
- C AU
- D AU
- E AU

**Q4: **

The flux density at a distance of 15.6 astronomical units from a star is 89.4 W/m^{2}.
What is the luminosity of the star? Give your answer in terms of the luminosity of the Sun to one decimal place.
Use a value of m for the length of 1 astronomical unit
and W for the luminosity of the Sun.

**Q5: **

A star has a luminosity of 4 . What is the flux density from the star at a distance of 3 AU? Use a value of W for the luminosity of the Sun and m for the length of 1 AU. Give your answer to the nearest watt per square meter.

**Q6: **

A star has a luminosity of W. What is the flux density of the star at a distance of m? Give your answer to one decimal place.

- A W/m
^{2} - B W/m
^{2} - C W/m
^{2} - D W/m
^{2} - E W/m
^{2}

**Q7: **

At what distance from the Sun is the flux density equal to
300 W/m^{2}?
Give your answer in astronomical units to two decimal places.
Use a value of
m
for the length of
1 AU
and
W
for the luminosity of the Sun.

**Q8: **

Sirius A is a nearby star with a luminosity of W. The luminosity of the Sun, , is W. What is the luminosity of Sirius A in terms of ? Give your answer to two decimal places.

- A
- B
- C
- D
- E

**Q9: **

The flux density at a distance of 0.7 AU from a star is 2,800 W/m^{2}. What is the luminosity of the star? Use a value of m for the length of 1 AU.
Give your answer in watts in scientific notation to two decimal places.

- A W
- B W
- C W
- D W
- E W

**Q10: **

Which of the following is the correct unit of luminous flux density?

- AW⋅m
- BW/m
- CW/m
^{2} - DW⋅m
^{2} - EJ/m
^{2}