MCQ Detailed View

A light-year is a special unit used to measure very large distances in space. It represents how far light can travel in one year through empty space. Light mo

how this distance is calculated:

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  Speed of light: 300,000 km/s

  
  


• 
  

  Seconds in a year: 60 × 60 × 24 × 365 = 31,536,000 seconds

  
  


• 
  

  Distance: 300,000 × 31,536,000 = 9.46 × 10¹² kilometers

  
  

This number is usually rounded to 9.5 × 10¹² km, which is the standard measurement for 1 light-year.

The term "light-year" helps s

ves incredibly fast, at a speed of about 300,000 kilometers per second (km/s). When we calculate the total distance it covers in a whole year, the value is enormous.

Here’scientists express the vast distances between stars, galaxies, and other objects in the universe. Using kilometers or miles for such distances would result in extremely large numbers, making them hard to understand or compare. That’s why light-years are more convenient for astronomical measurements.

For example:

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  The nearest star to Earth (other than the Sun), Proxima Centauri, is about 4.24 light-years away.

  
  


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  The Milky Way galaxy is roughly 100,000 light-years across.

  
  

Other options given in the MCQ are incorrect because:

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  9.5 × 10⁶ km and 9.5 × 10⁹ km are far too small.

  
  


• 
  

  9.5 × 10¹⁸ km is much larger than the real value.

  
  

Thus, the correct answer is Option C: 9.5 × 10¹² km, which represents the approximate distance light travels in a year.