Worksheet: Light-Years

In this worksheet, we will practice describing the distances between different objects that make up the Milky Way and the Universe.

Q1:

The speed of light is approximately 3 × 1 0 8 m/s. There are approximately 3 . 1 6 × 1 0 7 seconds in 1 year. Use these values to work out how far a beam of light will travel in 1 year. Give your answer to 2 significant figures.

  • A 3 . 2 × 1 0 7 m
  • B 9 . 5 × 1 0 1 4 m
  • C 9 5 × 1 0 1 5 m
  • D 9 . 5 × 1 0 1 5 m
  • E 6 . 2 × 1 0 1 5 m

Q2:

There are metres in 1 light year. What is m in light-years? Give your answer to the nearest light-year.

Q3:

There are metres in 1 light year. How many meters are there in 4 light years? Give your answer to 2 significant figures.

  • A m
  • B m
  • C m
  • D m
  • E m

Q4:

The Milky Way is about 1 0 0 0 0 0 light-years in diameter. 1 light-year is equal to 9 . 4 6 × 1 0 1 5 m . What is the diameter of the Milky Way in meters?

  • A 5 0 . 1 × 1 0 2 0 m
  • B 1 . 0 6 × 1 0 1 9 m
  • C 3 3 . 1 × 1 0 2 0 m
  • D 9 . 4 6 × 1 0 2 0 m
  • E 6 . 4 5 × 1 0 2 0 m

Q5:

A laser beam was fired off into space from an observatory on Earth’s surface. The beam was fired into an empty region of space, so it would not interact with anything. How far, in light-years, has the beam traveled 3 years later?

Q6:

The speed of light is approximately 3 × 1 0 / 8 m s . How far does a beam of light travel in 1 day? Give your answer to 2 significant figures.

  • A 7 . 2 × 1 0 9 m
  • B 1 . 2 × 1 0 1 2 m
  • C 3 . 2 × 1 0 1 1 m
  • D 2 . 6 × 1 0 1 3 m
  • E 6 . 6 × 1 0 1 5 m

Q7:

Which of the following is the correct definition of a light-year?

  • AA light-year is how long it takes a beam of light to travel the distance from Earth to the Sun.
  • BA light-year is how long it takes a beam of light to travel the same distance that Earth travels in 1 year.
  • CA light-year is the distance traveled by a beam of light in 1 second.
  • DA light-year is the distance traveled by a beam of light in 1 year.
  • E A light-year is how far light travels in half a year.

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