Unit 7 Waves, Sound, and Light

Unit 7 Waves, Sound, and Light

Chapter 20 The Energy of Waves

Section 1 The Nature of Waves

Wave a periodic disturbance in a solid, liquid, or gas as energy is transmitted through a medium

Medium a physical environment in which phenomena occur

Mechanical waves is waves that need a medium

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

Crest the highest point of a transverse wave

Trough the lowest point between each crest

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

Compression a part of longitudinal wave where the particles are crowded together

Rarefaction a part where the particles are spread apart

Surface wave combine of transverse and longitudinal waves, when waves from at or near the boundary between two media

Section 2 Properties of Waves

Amplitude the maximum distance that the particles of a wave’s medium vibrate from their rest position

Wave length the distance from any point on a wave to an identical point on the next wave

Frequency thenumber of waves produced in a given amount of time, expressed in hertz(Hz)

Wave speed the speed at which a wave travels through a medium

Section 3 Wave Interactions

Reflection the bouncing back of a ray of light, sound, or heat when the ray hits a surface that it does not go through

Refraction the bending of a wave as the wave passes between two substance in which the speed of the wave differs

Dispersion when light spread out into its separate colors

Diffraction a change in the direction of a wave when the wave finds an obstacle or an edge, such as an opening

Interference the combination of two or more waves that results in a single wave

Constructive interference when the crests of one wave overlap the crests of another wave or waves

Destructive interference when the crests of one wave and the troughs of another wave overlap

Standing wave a pattern of vibration that simulates a wave that is standing still

Resonant frequencies the frequencies at which standing waves are made

Resonance a phenomenon that occurs when two objects naturally vibrate at the same frequency; the sound produced by one object causes the other object to vibrate

Chapter 21 The Nature of Sound

Section 1 What Is Sound?

Vibration is the complete back-and-forth motion of an object

Sound wave a longitudinal wave that is caused by vibrations and that travels through a material medium

Tinnitus, common type of hearing loss, results from long-term exposure to loud sounds

Section 2 Properties of Sound

Pitch a measure of how high or low a sound is perceived to be, depending on the frequency of the sound wave

Ultrasonic soundsthat have frequency too high for people to hear

Doppler effect an observed change in the frequency of a wave when the source or observing moving

Loudness the extent to which a sound can be heard

Decibel the moist common unit used to measure loudness (symbol, dB)

Oscilloscope device that can graph representation of sound waves

Section 3 Interactions of Sound

Echo a reflected sound wave

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

Sonar is a type of electronic echolocation

Ultrasonography is a medical procedure that uses echoes to “see” inside a patient’s body without doing surgery

Sonic boom the explosive sound heard when a shock wave from an object traveling faster than the speed of sound reaches a person’s ears

Fundamental the lowest resonant frequency

Overtones higher resonant frequency

Section 4 Sound Quality

Sound quality the result of the blending of several pitches though interference

Noise a sound that consists of a random mix of frequencies

Chapter 22 The Nature of Light

Section 1 What Is Light?

Electromagnetic waves (EM) a wave that consists of electric and magnetic fields that vibrate at right angles to each other

Radiation transfer of energy as electromagnetic waves

Section 2 The Electromagnetic Spectrum

Visible light contains all of the colors that you can see

Electromagnetic spectrum all of the frequencies or wavelengths of electromagnetic radiation

Modulation changing amplitude or frequency

AM “amplitude modulation” FM “frequency modulation”

Radar is used to detected the speed and location of objects

Visible spectrum is range of colors

White light is visible light of all wavelengths combined

Section 3 Interaction of Light Waves

The law of reflection the law that states that the angle of incidence is equal to the angle of reflection

Incidence is the arrival of a beam of light at a surface

Regular reflection occurs when light beams are reflected at the same angle

Diffuse reflection occurs when light beams reflect at many different angles

Luminous objects that produce visible light

Illuminated a visible object that is not a light source

Absorption in optics, the transfer of light energy to particles of matter

Scattering an interaction of light with matter that causes light to change its energy, direction of motion, or both

Section 4 Light and Color

Transmission the passing of light energy or other form of energy through a matter

Transparent describes matter that allow light to pass through with little interference

Translucent describes matter that transmits light but that does not transmit an image

Opaque describes an object that is not transparent or translucent

Primary colors of light red, blue, and green

Color addition combining colors of light

Secondary color of light when two primary colors of light are added together

Pigment a substance that gives another substance or a mixture its color

Color subtraction mixing pigments

Primary pigments yellow, cyan, and magenta

Chapter 23 Light and our World

Section 1 Mirrors and Lenses

Plane mirror a mirror that has a flat surface

Virtual image is an image through which light does not travel

Concave mirror a mirror that is curved inward like the inside of a spoon

Real image is an image through which light passes

Convex mirror a mirror that is curved like the back of a spoon

Lens a transparent object that refracts light waves such that they converge or diverge to create an image

Convex lens a lens that is thicker in the middle than at the edges

Concave lens a lens that is thinner in the middle than at the edges

Section 2 Light and Sight

Nearsightedness a condition in which the lens of the eye focuses distant objects in front of rather than on the retina

Farsightedness a condition in which the lens of the eye focuses distant objects behind rather than on the retina

Color deficiency (colorblindness) happens when the cones in the retina do not work properly, cannot be corrected

Section 3 Light and Technology

Optical instruments are devices that use mirrors and lenses to help people make observations

Refracting telescopes use lenses to collect light(two convex lenses)

Reflecting telescopes use mirrors to collect light(plane mirror, concave mirror, convex lens)

Laser a device that produces intense light of only one wavelength and color

Amplification is the increase in the brightness of the light

Emission the release of photons

Stimulated emission occurs when a photon strikes an atom that is en an excited state and makes the atom emit another photon

Hologram a piece of film that produces a three-dimensional image of an object; made by using laser light

Optical fiber is a thin, glass wire that transmits light over long distances

Total internal reflection is the complete reflection of light along the inside surface of the material through which it travels

Polarized light consists of light waves that vibrate in only one plane

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