sound and light chapter 12. sound a longitudinal wave that spreads in all directions speed depends...
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Sound and Light
Chapter 12
Sound
A longitudinal wave that spreads in all directions
Speed depends on medium– Solids and liquids = quick movement– Gasses = slower movement– Increase temperature = increase speed
Intensity
Loudness of the sound– Increase amplitude = increase energy =
increase loudness = increase intensity– Increase distance = decrease intensity
Measured in decibels (dB)
Intensity
Pitch
Perceived loudness of a sound
Depends on frequency– Increase frequency = increase pitch
Infrasound vs. Ultrasound
Infrasound– Frequency below 20 Hz– Hard for human to hear (too low)
Ultrasound– Frequency above 20,000 Hz– Hard for human to hear (too high)
Uses of Sound
Sonar– Sound Navigation and Ranging– Reflect sound waves to show distance
Sonogram– Echoes (reflections) of very high frequency
sound waves – Can see inside animals
Are these infrasound or ultrasound?
Uses of Sound
Musical Instruments– Produce sound by vibrating air, solids, and
strings– Resonance helps produce the sound
• One vibrating object causes another object to vibrate
Light
Can be explained as waves– Electromagnetic waves– Spread in all directions– Used to explain most of the light we see
Can be explained as particles– A stream of tiny particles (photons) moving
very quickly
Speed of Light
Fastest in a vaccum– 3 x 108 m/s (186,000 mi/s)
Other speeds depend on the medium– Slows down in all cases– Gas is the fastest, then water, then
transparent solids
Intensity of Light
Brightness of light– Increase energy = increase brightness =
increase intensity– Increase distance = decrease intensity
Reflection of Light
Smooth surfaces reflection light in one direction
Flat surface
In-coming wave Incident wave
Out-going wave Reflected wave
Law of Reflection
Angle of incidence is equal to the angle of reflection
Flat surface
Incident angle
Reflected angle
Reflections of Light
Rough surfaces reflect light in many directions
Roughsurface
Reflection of Light
Mirrors can cause reflections to change– Flat mirrors create virtual images
• Image that appears to be behind or far away from where you are looking
– Curved mirrors create distortions (changes)
• Convex = bulge out = stretch image• Concave = curve in = compress image
Reflections
ConcaveConvex
Electromagnetic Spectrum
Light at all possible energies, frequencies, and wavelengths
Electromagnetic Spectrum
Bending of Light
Light will bend as it passes from one medium to another– Known as refraction
Happens in the air to create a mirage– A virtual image that happens mostly as the
atmosphere heats up
Bending of LightLight is made of all colors so it appears white
Can be bent through a prism to separate white light into all colors – Known as dispersion
Color of Objects
Objects have color because of what is reflected
All light hits an object– White light hits– Some colors absorbed– Some colors reflected -
this the color you see