Light Bending Into Water

In the picture

1. 1The green beam travelling through the air toward the tank.
2. 2The bright point where the beam meets the water surface.
3. 3The upright dashed line standing at right angles to the surface.
4. 4The faint dashed line showing the path the beam would have taken without changing direction.
5. 5The green beam inside the water, on its new steeper path to the tank floor.

Examples

• A straw in a glass of water looks broken or shifted at the surface.
• The bottom of a swimming pool looks closer to the surface than it really is.

Quiz: Light Bending Into Water (Age 15)

1. 1

   A narrow beam of light travelling through air meets the surface of a pool at a slant. What happens to the beam as it passes into the water?

   • It carries on in exactly the same direction as before.
   • It changes direction at the surface, then travels in a straight line along a new path.
   • It curves more and more, bending continuously as it goes deeper.
2. 2

   A beam enters water at a slant. Compared with the path it would have followed if its direction had not changed, where does the beam inside the water run?

   • Tilted further away from the line perpendicular to the surface, so it runs more sideways.
   • Exactly along that original path, because the water has no effect on it.
   • Tilted closer to the line perpendicular to the surface, so it runs more steeply downwards.
3. 3

   A beam of light hits the water surface head-on, at right angles to it. What happens?

   • It carries straight on into the water without changing direction.
   • It changes direction more sharply than a slanted beam does.
   • It is bent a little to the side, whatever angle it arrives at.

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.