P - Waves S2023

Study for the Learning Check! (OWL book will be available)

mechanical wave

a wave that travels through matter

electromagnetic waves

transverse waves that transfer energy through matter and the vacuum of space; travel their fastest in the vacuum of space at 300,000 km/s

electromagnetic spectrum

includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays

transverse wave

wave in which the particles of the medium move perpendicularly to the direction the wave is traveling

longitudinal wave

wave in which the particles of the medium vibrate parallel to the direction of wave motion

compression

part of a longitudinal wave where the particles of the medium are close together

rarefaction

part in a longitudinal wave where the particles are spread apart

water waves

these are a combination of transverse and longitudinal waves

seismic waves

mechanical waves that move through Earth's crust (P waves are longitudinal, S are transverse)

wavelength

horizontal distance between the crests or troughs

frequency

the number of wavelengths that pass a given point in one second; measured in Hertz (Hz)

amplitude

height of a wave; greater height = greater energy (and greater loudness for sound waves)

color

a quality produced by light waves; CASE 1: when light hits an object, some wavelengths are absorbed by the object and some are reflected; this quality is produced by the wavelengths of light reflected; CASE 2: if an object emits light itself, this quality is produced by the wavelengths it emits

additive color

color that is produced by light that is emitted directly from a light source (red, green and blue produce white)

subtractive color

color that is produced by the mixing of pigments (cyan, magenta, and yellow produce black)

white light

contains all the wavelengths of the visible spectrum

blue skies

As white light from the Sun enters Earth's atmosphere, much of the red, yellow, and green wavelengths of light (mixed together and still nearly white) pass straight through the atmosphere to our eyes. The blue and violet waves, however, are just the right size to hit and bounce off of the molecules of gas in the atmosphere. This causes the blue and violet waves to be separated from the rest of the light and become scattered in every direction for all to see. The other wavelengths stick together as a group, and therefore remain white.

red sunsets

As the Sun gets lower in the sky, its light passes through more of the atmosphere to reach you. Even more of the blue and violet light is scattered, allowing the reds and yellows to pass straight through to your eyes without all that competition from the blues.

cornea

convex lens made of transparent tissue located on the outside of the eye

iris

colored part of the eye that regulates size of pupil

eye lens

the transparent structure behind the pupil that changes shape (when ciliary muscles relax & contract) to help focus images on the retina

pupil

opening into the interior of the eye at the center of the iris

retina

layer of special light-sensitive cells in the back of the eye; where an image forms

rods

cells in the retina that are active in dim light

cones

cells in the retina that are active in bright light and detect color

sound wave

longitudinal wave caused by vibrations that only travel through matter (solids, liquids & gases)

speed of sound

increases with increasing temperature and/or density (faster in solids than gases); formula s=d/t

outer ear

collects sound waves

middle ear

amplifies sound waves

inner ear

converts vibrations to nerve signals that travel to the brain

pitch

perception of how high or low a sound seems

vocal cords

two membranes in the throat that vibrate creating sound waves; muscles connected to these make them thicker and thinner like guitar strings

decibel scale

measures loudness of sound

sonar

uses reflected sound waves to locate objects under water

echolocation

the process of using reflected sound waves to find objects used by animals such as bats and dolphins

standing wave

waves that appear to be standing still

node

a point on a standing wave that has no displacement from the rest position

antinode

a point of maximum displacement midway between two nodes in a standing wave