refraction: review: what is refraction? why does it...
TRANSCRIPT
Lesson 3Refraction and Lenses
Refraction:
Review: What is refraction?
Why does it happen?
Lesson 3Refraction and Lenses
Refraction is the change in direction of light. It occurs because light travels at different speeds through different materials.
Lesson 3Refraction and Lenses
Your activity allowed you to explore how light refracts in other liquids.
What happened?
Lesson 3Refraction and Lenses
We know light travels at different speeds through different materials.
The measure of how much the speed of light is reduced in different materials is called the refractive index.
The higher the refractive index, the more it bends towards the normal.
Lesson 3Refraction and Lenses
Remember when we looked through curved mirrors, the image might have been reflected a different size or upside down?
Do you remember which mirrors gave each type of image?
Lesson 3Refraction and Lenses
Remember when we looked through curved mirrors, the image might have been reflected a different size or upside down?
Do you remember which mirrors gave each type of image?
Convex: image is right side up but smaller than object.
Concave: When object is further away from the mirror, the image is small and upside down.
When object is close to the mirror, the image is bigger but right side up.
Lesson 3Refraction and Lenses
The mirrors had different effects on the reflected image because they are curved.
In the same way, the shape of a block of glass that light passes through has an effect on the refracted image.
A lens is a piece of transparent material (glass, plastic) with at least one curved surface.
Where have you seen a lens before?
Lesson 3Refraction and Lenses
Types of Lenses:
Think about a magnifying glass, do we use a convex lens or concave lens to make magnify something? (Make it appear bigger)
Lesson 3Refraction and Lenses
From your booklet:
Holes that let in light:
In the eye: pupilIn a camera: aperture
Controls the amount of light that can enter the lens/eye:
The pupil is surrounded by a band of muscle called the iris which controls the size of the pupil.
Diaphragm changes the size of the aperture.
Reacts to the light entering:
When light hits the retina, receptor cells send messages to the brain which are translated into an image.
The CCD matrix reacts to the light and pixrls are illuminated.
Lesson 3Refraction and Lenses
Fixing problems with lenses
What is the one most common problem we easily fix with a lens?
Lesson 3Refraction and Lenses
Fixing problems with lenses
What is the one most common problem we easily fix with a lens?
Our sight!
People wear glasses or contact lenses because their eyes do not focus images on their retina properly.
The two most common problems are myopia (nearsightedness) and hyperopia (farsightedness)
Notice that the image is focused too soon for myopia and too late for hyperopia. So lenses are used to refract the light more or less so that it gets focused in the right spot.
Lesson 3Refraction and Lenses
Lesson 3Refraction and Lenses
Animals' sight is very different than ours!
Horses and zebras have excellent peripheral vision so they can see predators from many directions. However, they do have a blind spot directly in front of their noses.
Deer can only see the colors blue and green.
Dogs and cats are color blind but have better peripheral vision and night vision than humans do.