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 3.83×10 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 1.50×10 m for the length of 1 AU. Give your answer to two decimal places.

Q2:

Star A has a luminosity 𝐿 and star 𝐵 has a luminosity 𝐿=4𝐿. At a distance 𝑑 away from star 𝐴 and a distance 𝑑 away from star 𝐵, the flux densities due to each star are equal. What is the ratio 𝑑𝑑?

  • A1
  • B2
  • C12
  • D4
  • E14

Q3:

The Peony star, which is located near the galactic center, has a luminosity of 3.2×10𝐿. At what distance from this star is the flux density equal to the flux density from the Sun at Earth? Use a value of 1.50×10 m for the length of 1 AU and 3.83×10 W for the luminosity of the Sun. Give your answer in scientific notation to two decimal places in astronomical units.

  • A1.54×10 AU
  • B1.79×10 AU
  • C2.68×10 AU
  • D1.54×10 AU
  • E1.79×10 AU

Q4:

The flux density at a distance of 15.6 astronomical units from a star is 89.4 W/m2. 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 1.50×10 m for the length of 1 astronomical unit and 3.83×10 W for the luminosity of the Sun.

Q5:

A star has a luminosity of 4 𝐿. What is the flux density from the star at a distance of 3 AU? Use a value of 3.83×10 W for the luminosity of the Sun and 1.5×10 m for the length of 1 AU. Give your answer to the nearest watt per square meter.

Q6:

A star has a luminosity of 7.6×10 W. What is the flux density of the star at a distance of 1.5×10 m? Give your answer to one decimal place.

  • A1.1×10 W/m2
  • B5.4×10 W/m2
  • C2.7×10 W/m2
  • D4.0×10 W/m2
  • E1.6×10 W/m2

Q7:

At what distance from the Sun is the flux density equal to 300 W/m2? Give your answer in astronomical units to two decimal places. Use a value of 1.50×10 m for the length of 1 AU and 3.83×10 W for the luminosity of the Sun.

Q8:

Sirius A is a nearby star with a luminosity of 9.73×10 W. The luminosity of the Sun, 𝐿, is 3.83×10 W. What is the luminosity of Sirius A in terms of 𝐿? Give your answer to two decimal places.

  • A12.60𝐿
  • B0.04𝐿
  • C25.40𝐿
  • D0.25𝐿
  • E3.94𝐿

Q9:

The flux density at a distance of 0.7 AU from a star is 2,800 W/m2. What is the luminosity of the star? Use a value of 1.50×10 m for the length of 1 AU. Give your answer in watts in scientific notation to two decimal places.

  • A1.98×10 W
  • B3.88×10 W
  • C9.70×10 W
  • D7.92×10 W
  • E5.66×10 W

Q10:

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

  • AW⋅m
  • BW/m
  • CW/m2
  • DW⋅m2
  • EJ/m2

This lesson includes 1 additional question for subscribers.

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