Objectives- Explain how different shape objects (lenses) refract light
Light can be bent or refracted.
This is caused by light changing speed as it pass through an object (medium) to another at an angle. As it changes speed, it becomes bent and changes the path it is taking. This is called refraction. You have probably noticed that a straw appears to be broken when you look at it in a glass of water. This is because the light travelling through the water travels at a different speed than light travelling through air and the straw appears to be broken. This makes it hard to shoot fish with a bow and arrow. Since the light has been bent due to it changing speed is it passes through the water, the fish it not where it appears to be. When light passes from one medium to another it changes speed.
The amount light changes speed depends on the wavelength. For example, red light has a different wavelength than blue and it will bend a different amount. That is why when light passes through a prism such as water, you see a rainbow. Each of the wavelengths in white light is refracted a different amount and comes out in a different place.
The amount light is bent is also affected by the medium it passes through. Some mediums refract light more than others. This is one property that can be used to identify many minerals- how much they bend light. Cubic zirconia bends light less than diamonds and will produce less sparkle!
Lenses are pieces of glass that bend light.
Convex lenses are fatter in the middle compared to the ends. When light passes through a convex lens, it gets bent inwards to a focal point. The focal point is where the light converges, or comes together. How far away the focal point is from the lens depends on how curved the lens is. If it is curved a lot, light will bent more and the focal point will be closer to the lens.
Concave lenses are thinner in the center. They cause light to bend outwards, or diverge. How much light is scattered depends on how much the lens is curved.
When light passes through a raindrop, it changes speed. Water is a different medium. Each wavelength (color) of light is refracted, or bent, a different amount.
Each color comes out at a different place. Remember, white light is a mixture of seven different wavelengths. A rainbow allows you to see each one.
Define refraction

How are convex lens shaped?
What do convex lenses do to light?
What is a focal point?
How is a concave lens shaped?
What does a concave lens do to light?
How does a rainbow form?
What do eyeglasses to do light?