Sound & Light Waves

SOUND

I. Compressional Waves A. Recall Sound Waves are compressional waves and create compressions & rarefactions. B. Sound waves also move faster through solid mediums & at warmer temperatures

II. Amplitude & Energy of Sound A. The amount of energy a wave carries correlates with the waves amplitude. 1. Higher the amplitude louder the sound. Resulting in larger compressions & rarefactions 2. Loudness is all about human perception

Interference Two waves overlap and combine to form a new wave. Instrumentalists/vocalists you hear this when the group harmonizes and another note comes through.

III. Intensity A. The intensity of a sound wave, or amount of energy transferred through a certain area, has to deal with how close you are to the source of the sound. 1. Farther from the source intensity decreases since the energy transferred decreases & waves have spread out B. The scale to measure intensity uses the decibel (dB). It ranges from 0-150

IV. Pitch & Frequency A. Pitch is the human perception of sound when frequency of sound waves changes. 1. Frequency is measured in Hertz(Hz) and our range is from 20-20,000 Hz B. Waves that fall above these frequency are called ultrasonic & waves that fall below are infrasonic (subsonic) 1. Ex. Dog whistle vs. earthquake rumble

V. Using Sound A. The Doppler effect is any change in frequency/pitch of a sound wave due to relative motion of the wave source. 1. Can be used to establish how quickly a source is moving away or towards you B. Sound can also be used to locate objects around the source. (reflection) 1. Echolocation, SONAR & Ultrasounds

LIGHT

I. Interaction of Light & matter A. To be able to detect objects around you they need to reflect & emit some light that reaches your eye.

II. Absorption, Transmission & Reflection A. Materials that are opaque can only absorb & reflect light B. Material that allows some light to pass through are called translucent C. Transparent materials transmit all the light striking them, only some light is absorbed & reflected/refracted.

III. Reflection of Light A. Recall Law of Reflection B. The smoothness of the surface that does the reflection will determine how sharp the reflected image will be. 1. The smoother the surface the clearer the reflection. The rougher a surface is, the more diffuse the reflection will be & can eventually result in scattering.

IV. Refraction A. Recall refraction occurs when light waves change speeds because of the medium it travels in. 1. The larger the difference in speed the more refraction (Index of refraction) Ex. Mirages (water in the distance), Pencil in water

V. Diffraction A. Diffraction occurs when an object causes a wave to change direction and bend around it. 1. Only when a wave passes around an object does diffraction occur B. Amount of diffraction that occurs depends on the size of obstacle or opening. 1. Waves that have a larger wavelength than the object will bend around if object is larger waves will NOT diffract.

EYES

I. The Eye A. Light enters your eye through the cornea. The cornea causes light to bend & converge. B. The light then passes through your pupil & a flexible convex lens. 1. Muscles attached to the lens change the shape to help focus the light C. The retina is the inner layer of your eye that is full of light-sensitive cells that convert an image to be sent to the brain.

II. Brightness & Intensity A. The eye has the ability to adjust to the brightness of light that strikes it by dilating or shrinking the size of your pupil. 1. How close you are to the source of light is going to determine the intensity of light & how much your pupil has to be adjusted

III. Vision Problems Farsightedness Nearsightedness Near objects appear blurry because the eye is to short & the image is focused behind the retina Fix with convex lens Nearsightedness Far objects appear blurry because the eye is to long & the image is focused in front of the retina Fix with concave lens

IV. Seeing Color Cones Rods Allow you to see color in only bright areas Red, Green & Blue cones Rods Allow you to see in both dark & bright areas