Chapter 11 Sound and Light Beginning on page 35 of your packet.

Section 1 Sound A. Sound waves form when a vibrating object collides with air (or any kind of) molecules transferring energy to them.

Section 1 Sound 1. Compressional waves have two regions, called compressions and rarefactions, which push air molecules together and then spread them apart.

Compressional Wave

Section 1 Sound A sound wave’s speed depends on the temperature and state of the medium. 1. Sound travels more quickly through solids and liquids; the molecules are closer together than those in gas.

Section 1 Sound 2. As a medium’s temperature rises, its molecules move faster, conducting sound waves faster.

Section 1 Sound C. The amount of energy a wave carries corresponds to its amplitude, which is related to the density of the particles in the compressions and rarefactions.

Section 1 Sound D. Intensity – the amount of energy that flows through a certain area in a specific amount of time.

Section 1 Sound Loudness – human perception of sound intensity. Each unit on a scale that measures sound intensity is a decibel.

Section 1 Sound Pitch – how low or high a sound seems to be (dog whistler) Frequency is the number of compressions or rarefactions of a sound wave that pass per second; humans can hear 20-20K

Section 1 Sound Ultrasonic – waves have sound frequencies over 20,000 Hz that have medical and other uses. Subsonic – waves with f below 20 Hz: rumble

Section 1 Sound F. Doppler effect – change in pitch or wave frequency due to a moving wave source (or to the movement of the listener).

Section 1 Sound G. Echolocation – process of locating objects by sending out sounds and interpreting the waves reflected back. Where might you find this in nature?

Section 1 Sound Sonar – a system that uses the reflection of underwater sound waves to locate objects. Ultrasound waves are used in medicine to diagnose, monitor, and treat many conditions.

Escape

Section 2 Reflection and Refraction of Light Light and matter – objects must reflect light to be seen. 1. Opaque materials do not allow light to pass through them; they only absorb and reflect light.

Section 2 Reflection and Refraction of Light Some light passes through translucent materials (like the light coverings in D-5). Transparent materials transmit all light, absorbing and reflecting little light.

Section 2 Reflection and Refraction of Light Law of reflection – the angle at which light strikes a surface equals the angle at which it is reflected. 1. Regular reflection-reflection of light waves from a smooth surface.

Section 2 Reflection and Refraction of Light Diffuse reflection-reflection of light waves in many directions from a rough surface. Scattering-type of diffuse reflection that occurs when light waves traveling in one direction are made to travel in many different directions.

Section 2 Reflection and Refraction of Light Refraction of light-change in the speed of light wave when it passes from one material to another. 1. The index of refraction indicates how much a material reduces the speed of light; the more the light is slowed, the greater the index of refraction.

Section 2 Reflection and Refraction of Light Prisms separate white light into visible spectrum based on light wavelengths. Refraction of light through air layers of different densities can result in a mirage.

Section 2 Reflection and Refraction of Light Discussion question: Why can’t you see an object in the dark?

Section 2 Reflection and Refraction of Light Discussion question: Why can’t you see an object in the dark? Answer: Objects must reflect light to be seen.

Section 3 Mirrors, Lenses and the Eye Light waves spread in all directions from a light. Mirror – any surface that produces a regular reflection.

Section 3 Mirrors, Lenses and the Eye Plane mirror – flat, smooth mirror in which an image appears upright. In a concave mirror, the mirror surface is curved inward; the image depends on location of object relative to focal point.

Section 3 Mirrors, Lenses and the Eye Convex mirrors are curved outward, diverge light rays when reflected, and show virtual images. C. Lens – transparent material with a curved surface that refracts light rays.

Section 3 Mirrors, Lenses and the Eye A convex lens is thicker in the middle than at the edges. a. Form real, reduced, and inverted image when object is more than two focal lengths from the lens.

Section 3 Mirrors, Lenses and the Eye Form real, enlarged, and inverted image when object is between one and two focal lengths from the lens. Form virtual, enlarged, and upright image when object is less than one focal length from the lens.

Section 3 Mirrors, Lenses and the Eye A concave lens is thinner in the middle and thicker at the edges. D. The structure of your eye allows you to focus on objects.

Section 3 Mirrors, Lenses and the Eye Light enters the eye through the cornea, a transparent covering on the eyeball. A convex lens helps to focus light rays to form sharp images.

Section 3 Mirrors, Lenses and the Eye Retina – inner lining of the eye that converts light into electrical signals that the brain interprets. E. Vision problems occur when lenses in the eye do not focus images properly.

Section 3 Mirrors, Lenses and the Eye Farsightedness – when lens is not curved enough to form an image of close objects. Astigmatism – the cornea’s surface is unevenly curved.

Section 3 Mirrors, Lenses and the Eye 3. Nearsightedness – lens does not flatten enough to form an image of distant objects.

Section 3 Mirrors, Lenses and the Eye Discussion Question! What are three shapes of mirrors?

Section 3 Mirrors, Lenses and the Eye Discussion Question! What are three shapes of mirrors? Answer: Plane (flat), concave (curved inward) and convex (curved outward).

This Time…

Section 4 Light and Color A. Color is determined by the wavelength of light an object reflects. 1. Objects appear to be white because they reflect all colors of visible light.

Section 4 Light and Color 2. Objects appear to be black because they absorb all colors of visible light.

Section 4 Light and Color 3. Filter – transparent material that absorbs all colors except the one it transmits.

Cool Science Explanation. Can you explain why the image of the Sun appears reddish at sunrise and sunset?

The sunlight has to travel through more atmosphere at dawn and dusk. The atmosphere refracts more light at these times.

Section 4 Light and Color Light enters the eye and is focused on the retina, which absorbs light. 1. Cone cells – distinguish colors and detailed shapes; most effective in daytime vision.

While humans have three types of color-detecting cells, mice and most other mammals have just two. But when a group of scientists gave mice the human gene for a third color detector, they were able to detect colors that no mouse has ever seen before.

Section 4 Light and Color Rod cells – sensitive to dim light; most effective in nighttime vision. Color blindness results when one or more sets of cones do not function properly.

Section 4 Light and Color All colors of light are made by mixing the three primary colors of red, green, and blue. 1. Primary colors of light are additive and combine to form white light.

Section 4 Light and Color Pigment – colored material that absorbs some wavelengths of light and reflects others. 1. Primary colors of pigment are magenta, cyan and yellow.

Section 4 Light and Color 2. Primary colors of pigment are subtractive and combine to form black.

Section 4 Light and Color Discussion Question: What would happen if none of the cones in a person’s eye worked properly?

Section 4 Light and Color Discussion Question: What would happen if none of the cones in a person’s eye worked properly? Answer: The person would not see color.

Now, to see if YOU are colorblind… In your notes, write down the numbers, letters or symbols you see in the next slides. Please, no talking or peeking.

The End!