Learning Goals:
Refraction is the bending of light when it crosses a boundary between two substances.
Refraction is used in communications and other technologies.
Success Criteria: I can…
…state the definition of refraction.
…explain why refraction occurs.
…discuss technologies that employ refraction.
Refraction & Light Waves
The bending effect of light when it crosses a boundary between two different media is called refraction.
Thus, refraction is defined as the change in the direction of light when it crosses a boundary between two media.
The medium is the substance through which light is travelling; the plural is media. In the above example, the media are air and water.
When light travels from one medium into another at an angle, the difference in the speed of the light causes a change in the direction of the light.
Notice that light passes through the boundary and that the angle of incidence ≠ the angle of refraction.
This is what cause the pencil in water (in the picture above) to look wacky when viewed from certain angles.
What Causes Refraction
Light refracts because light travels at different speeds in different media.
To understand why the light ray bends the way it does, imagine a car travelling along a surface.
Look at A in the image above: If the car travels from smooth pavement onto a muddy surface, it’s speed will decrease. This causes the car to turn in toward the normal line.
When dealing with two media, we say that that when light travels from an optically less dense medium to an optically more dense medium, it bends toward the normal.
Look at B in the image above: If the car travels from a muddy surface onto smooth pavement, it’s speed will increase. This causes the car to turn in away from normal line.
When dealing with two media, we say that that when light travels from an optically more dense medium to an optically less dense medium, it bends away from the normal.
This video (watch from 3:40 to 5:43) uses a similar analogy to explain the above.
Question of the Day #10: Explain how refraction is different from reflection. Send me your answer on Edsby.
