Maud stands a straw in a glass of water. At the water's surface the straw looks broken: the part below the surface seems tilted at a new angle.
The straw is straight. What changed direction is the light coming from it. This lesson names that behavior for light.
Light from the underwater part of the straw travels up through the water, crosses the water's surface, and continues through the air to Maud's eye.
At the surface, the light's direction changes.
The surface is a boundary: water on one side, air on the other.
You saw refraction for water waves in the waves topic: ripples change direction as they cross into shallower water. Light refracts in the same sense: a direction change at a boundary.
In earlier grades you saw that light arriving at a material can be reflected, absorbed, or transmitted. Refraction happens to the transmitted light: the light that crosses into the new medium.
Refraction happens at the boundary, not inside the new medium. Once the light is fully inside one medium, it travels in a straight line again, in its new direction.
That is why the straw looks broken: the light from the underwater part reaches the eye along a bent path, so the underwater part appears shifted.
A coin rests on the bottom of a fountain. Nilo looks at it from the edge. Light from the coin changes direction as it leaves the water. Name the behavior.
The light crosses a boundary between two media: water below, air above.
At that boundary, its direction changes.
A direction change where light crosses a boundary between two media is refraction.
The behavior is refraction.
A flashlight beam shines through the side of an aquarium: air, then the glass wall, then the water. At how many places can the beam's direction change?
Refraction happens where light crosses a boundary between two different media.
The beam crosses two boundaries: air into glass, then glass into water.
Each crossing is a boundary between two different media.
The direction can change at two places: the air-glass boundary and the glass-water boundary.
A laser beam changes direction as it passes from air into a block of clear gelatin. Which behavior is this?
A beam travels through air, enters a plastic block, and travels on inside the plastic. Where can its direction change?
Nilo says: 'Light can change direction without bouncing off anything: crossing into a different medium can bend its path.' Is Nilo correct?
Which statement defines refraction of light?
Sunlight strikes a still pond. Part of the light bounces up off the surface, and part enters the water with its direction changed. Which part shows refraction?
In a salad-dressing bottle, a beam of light passes from the oil layer down into the vinegar layer. Which statement is true?