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 10 8 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 Rough surface

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 Concave Convex

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 Light Light 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