Light and Sound Notes

How Materials Transmit Light

• Transparent – allows most light to pass through

• Translucent – transmit some light, but also cause it to spread in all directions. You see light through the object, but can not see objects clearly.

• Opaque – no light is allowed to pass through because they reflect or absorb light.

Scattering

• Spreading out of light rays in all directions, because particles reflect and absorb the light.– Fog or dust in the air, mud in water, smudges on glass.

• Scattering makes the sky blue during the day because our atmosphere scatters blue more than the other colors. What color is present in the morning and evening?

Wavelengths Determine Color: Light

• Your eye can only detect 3 color bands: red, green and blue. Your brain perceives these colors and the mixtures of these colors. These three colors of light are called primary colors.

• When red, green & blue light are mixed in equal proportions (added together), the 3 primary colors yield white light because they are being reflected.

• When you mix any 2 primary colors, you make a secondary color. a. Green + Red = Yellow b. Green + Blue = Cyan c. Blue + Red = Magenta

Wavelengths Determine Color: Pigment

• The Primary Pigments are magenta, cyan and yellow. Secondary Pigments are red, blue and green.– When mixed in equal proportions (added together), the 3 secondary

colors produce black because all colors are being absorbed.

• If I shine green light on a red apple, what color

will the appear?

BLACK!!!!!!!

• Why? • In white light, a red apple absorbs all the colors

(including green) of the spectrum except red, which it reflects. A green transparent filter absorbs (or subtracts) all the colors of the spectrum except green, which is transmitted through the filter (and comes through as green light).When the green light shines on a red apple, the red apple absorbs the green light. Since there is no red light shining on the apple, there is no red light to reflect, so the apple appears black.

Sound• Sound is a type of mechanical wave.• Vibrations are required to start a sound wave.– Your vocal chords

Sound can not travel in a vacuum

The Speed of Sound Depends on it’s Medium.

• Sound can travel through a solid, liquid and gas.

• Sound travels fastest through a solid because of refraction. The molecules are closer together, so it bounces faster. Think about a pinball machine.

Does Temperature Effect Sound?

• YES!!!!!• The higher the temperature, the faster sound

will move.• On a hot day, you will hear people clearer than

on a cold day.

Frequency Determines Pitch

• Pitch is the highness or lowness of a sound.• The faster the vibration, the higher the sound.• The highest frequency humans can hear is

20,000 hertz.• The lowest is around 20 hertz.

Doppler Effect

• Is the change in perceived pitch that occurs when the source of the sound is moving.

• https://www.youtube.com/watch?v=WCEhidp8tiA

Doppler Effect

• https://www.youtube.com/watch?v=0rJPvGML9A0

Amplitude Effects Loudness

• If you increase the amplitude of a wave, the sound will become louder.

• The opposite is also true. If you decrease the amplitude of a wave, the sound will become softer.

Think of frequency as pitch and amplitude as volume.

• https://www.youtube.com/watch?v=YTZcSaPn92s