Objective Although convex and concave lenses are concrete objects, the notion of what they do to light rays is very abstract.
This lesson will give concreteness to the path of light through lenses. It will show the principal of light refraction and how this is done on an angle. It will also show that light rays are straight. This lesson will help students understand how the x-ray technician is able to acquire accuracy when taking a radiograph. It will help students to know that the light beam emitted from the x-ray machine will be emitted in a straight line, thus allowing the technician great area accuracy.
Materials Needed Fifty pound fish tank, water, iodine or mercurochrome, a flashlight with a slit over the glass.
1. Place a 50-L fish tank on a table. Fill it with water to about 5 cm. from the top. Color the water with iodine or mercurochrome.
2. Fit a flashlight with a top that has a slit over the glass.
3. Shine the light straight down into the water.
4. Shine the light at a slant through the water (for refraction).
Observations and Analysis
1. When the light shines straight down into the water, the light beam is straight.
2. When the light sines into the water at a slant, the light beam bends.
3. All surfaces of matter reflect light. Light is bent when it passes at a slant from one transparent material to another transparent material.
4. Light can be bent (refracted) when it is slowed down or speeded up.