• Question: How come light travels easier in air than in glass?

    Asked by anon-257396 to Georgia on 25 Jun 2020.
    • Photo: Georgia Harris

      Georgia Harris answered on 25 Jun 2020:

      Hey Abett, great question!
      +
      Light *always* travels at the same speed.
      However, in a material like glass, there are lots of molecules packed closely together compared to the spread out molecules that form air. So when light passes through glass, it takes longer to get from one side to the other because it’s bouncing off more molecules.
      +
      It’s like if you ran across the playground but in one situation the playground is empty and in another situation it’s full of school children playing. Even if you ran at the same speed, it would take you longer to get from one end to the other when you have to dodge the other people in your way. (:

Comments

  • Photo: Jessica

    Jessica commented on :

    Hi Abett, great question! Light is still travelling at the same speed but it gets scattered by molecules as it passes through a medium. In glass, the molecules are more densely packed than in air, so it takes light longer to pass through. The light also gets refracted (it changes direction) when it enters glass. You can think of it light travelling through air like a car driving on a smooth road. If the car hits a sandy beach, it will ‘slow’ down’ and change direction. This is what happens to light when it hits glass.