One of the most important uses of reflection involves lenses. By controlling how much, and in what direction, light bends we are able to see, heat objects and send information. A lens is simply a refracting object with a curved surface. The two main types of lenses are convex and concave.
Investigating Refraction Through Lenses
Aim: To investigate how different types of lenses refract light.
Equipment:
- Triple-split ray slide
- Power supply
- Concave lens
- Convex lens
Method:
- Set up a ray box, triple-slit ray slide and power supply.
- Place the convex lens and place the ray box near the convex lens, and shine the three rays of light at the lens. Make sure the central light hits the lens at 90° as indicated in the diagram.
- Carefully trace the direction of the incoming ray and refracted rays.
- Repeat using the concave lens.
Results:
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| Convex Lens |
 |
| Convex Lens |
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| Concave Lens |
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| Concave Lens |
Conclusion:
The following sentences describe the way light refracts through the two different lenses. Read the sentences and identify which lens relates to each sentence.
When light passes through this type of lens, the rays all move away (diverge) from each other. One use of these lenses is in security peepholes in a door so that a person inside a room can see who is at the door without having to open it.
1. The lenses described in the paragraph above is a concave.
When light passes through this type of lens, the rays all move towards (converge) each other. One use of these lenses is in a camera, to focus the light onto the film or digital sensor. Magnifying glasses also use this type of lenses.
2. The lens described in the paragraph above is a convex.
