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The Human Body

The Human Body. Chapter Twenty: Vision and Hearing. 20.1 The Nervous System 20.2 Color Vision 20.3 Light and Images 20.4 Hearing. 20.3 Reflection. Light given off from objects like a light bulb or the Sun travels in straight lines.

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The Human Body

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  1. The Human Body

  2. Chapter Twenty: Vision and Hearing • 20.1 The Nervous System • 20.2 Color Vision • 20.3 Light and Images • 20.4 Hearing

  3. 20.3 Reflection • Light given off from objects like a light bulb or the Sun travels in straight lines. • We can show how light travels using imaginary lines called light rays.

  4. 20.3 Reflection • Reflectionoccurs when light bounces off of a surface. • Imagine a light ray striking a mirror.

  5. 20.3 Law of Reflection • The incident rayis the light ray that strikes the surface of the mirror. • The reflected rayis the light ray that bounces off the surface of the mirror. • The angle of incidence is always equal to the angle of reflection.

  6. 20.3 Refraction • Refractionis the bending of light as it crosses a boundary between two different transparent materials. • As light passes from one type of matter into another, it will change speed and bend.

  7. 20.3 Refraction • When a light ray traveling through air enters glass it slows down and refracts, bending toward the normal line.

  8. 20.3 Refraction • When light goes from glass to air, it speeds up, bending away from the normal line. • This bending effect takes place whenever light slows as it moves from one material into another.

  9. 20.3 Refraction • A glass rod in water is a good example of refraction. • The glass rod appears to break where it crosses the surface of the water. • This illusion is created because light is refracted as it travels from air to water.

  10. 20.3 Lenses • A lensis an object that is designed to refract light in a specific way. • Many devices you use contain lenses. • There are two basic kinds of lenses: convex and concave.

  11. 20.3 Convex lenses • Light rays that enter a convex lens parallel to its axis refract and meet at a point called the focal point. • The distance from the center of the lens to the focal point is the focal length.

  12. 20.3 Concave lenses • Light rays that enter a concave lens parallel to its axis refract and spread out as they exit the lens. • The focal point of a concave lens is located on the same side of the lens as the light source.

  13. 20.3 Virtual and real images • In a virtual image, light rays do not actually come together to a focal point to form the image. • They only appear to come together. • Virtual images are illusions created by your eye and brain.

  14. 20.3 Virtual and real images • In a real image, light from a single point on an object comes back together at a single point in another place to make an image. • A convex lens can form a real image.

  15. 20.3 How the human eye forms an image • The pupilis an opening created by the iris, the pigmented part of the eye. • A ring of muscles causes the iris to open or close to change the size of the pupil.

  16. 20.3 How the human eye forms an image • The lens in your eye has a feature that makes it different from the lenses you use in a science lab. • The lens in your eye is flexible and can change its focal length.

  17. Investigation 20B The Human Eye • How does the human eye form an image?

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