1. Sound
Properties of Sound
Speed depends on medium
Sound travels faster in liquids and solids -> particles are closer.
Speed of sound in air is 760 mph.
Some solids (rubber) dampen vibrations -> so it moves slower.
Loudness is based on intensity.
Intensity – describes loudness at a distance from the source.
Deals with decibels, Fig 12-2.
Pitch – perceived highness or lowness of a sound, based on frequency of the wave.

2. Humans have limited hearing range
Our range: 20 Hz – 20,000 Hz.
Below 20 Hz = infrasound
Above 20,000 Hz = ultrasound
Hearing and the Ear
Ear senses vibrations in the air, amplifies them, and then transmits signals to the brain. Fig 12-7
Sound passes through 3 regions:
Outer ear (outside your head)
Middle (ear drum, hammer, anvil, stirrup)
Inner (cochlea)

3. Ultrasound and Sonar
Sonar – reflecting sound waves off an object to determine distance and location.
Ex: tracking submarines and ocean mapping.
Ultrasound used in medicine.
Ex: baby images, organ viewing, to guide surgical procedures.
Nature of Light
Waves and Particles
Light behaves like a wave and particle
Modeled like a wave (Figure 12-10)
Creates interference.

4. Modeled like a stream of particles.
Photons – particle of light.
a.Do NOT have mass -> not matter.
b.Bundles of energy.
Light energy is related to frequency
High energy = high frequency (gamma rays and X-rays)
Low energy = low frequency (radio waves)
Light’s speed depends on its medium.
Brightness depends on intensity.

5. Electromagnetic Spectrum
Gamma + X-rays – highest energy, used in medicine and cancer treatment.
Ultraviolet light – high energy, causes sunburn; three types (UV – A,B,c)
Infrared – felt as warmth or heat, low energy.
Microwaves – cooking and communicating, low energy.
Radio waves – radar and communications, low energy.
Reflection and Color
Reflection of light
Rough surface => reflects in many directions.

6. Smooth surface => reflects in one direction.
Figure 12 – 19.
Mirrors
Flat mirror:
Forms virtual image (image forms from light appearing to come from behind but actually doesn’t.)
Curved mirror:
Forms distorted image b/c light photons are reflected in different directions.
Convex vs. concave:
Convex – mirrors that bulge out.
Concave – mirrors that are indented.

7. Seeing color
An object’s color is the color that is reflected.
Black => all colors are absorbed (R,O,Y,G,B,V).
White => all colors reflected equally.
Colors my add or subtract to produce other colors.
Figure 12-24
Figure 12-25
Refraction, Lenses, and Prisms
Refraction
Creates images that appear to be in different positions. (Figure 12-29)
Creates mirages. (water on the road)

8. Total internal reflect – angle at which light rays meet the boundary between two mediums becomes large enough, the rays will be reflected not refracted. Figure
Fiber-optics carry data or signals this way.
Lenses – refracts light rays, causing them to converge or diverge to create an image.
Converging – bends light inward; creating a real or virtual image.
Diverging – bends light outward; creates only a virtual image.
Magnification – change in the size of an image.
Microscopes and telescopes have multiple lenses.

9. Vision in your eyes: Figure 12-35
Light is refracted by the cornea into the pupil.
Light passes through the lens, which change to focus the image at the back of the retina.
Image is sent to the brain as a signal.
Prisms Figure 12-36
Different colors refract at different angles creating a “rainbow.”