Light and Sound

Name:Test date:

Light & Sound Table of contents1._____________________2._____________________3. ____________________4. ____________________5. ____________________6. ____________________7. ____________________8. ____________________9. ____________________10. ___________________11. ___________________12. ___________________13. ___________________14. ___________________15. ___________________

Name__________________________Light & Sound Study Guide

Tentative Test Date:

Light EnergyEmit When an object gives off light it has producedEnergy The ability to do “work”. How things change and moveLight Ray Light energy travels in straight lines called rays until it hits an object where it is reflected,

refracted, transmitted or absorbedLight Source Something that gives out energy in the form of electromagnetic waves in the visible

spectrum can be natural, like the sun or artificial, like electric lamps.

Radiate When energy travels by electromagnetic waves. Light radiates from its source, or travels from it in transverse waves.

Visible Light or Visible Spectrum

Only waves with certain wavelengths can be seen by the human eye. Includes the colors of the rainbow (ROYGBIV):

Red (lowest frequency that can be seen) Orange Yellow Green Blue Indigo Violet (highest frequency that can be seen)

Infrared Waves with frequencies slightly lower than red are called infrared, and cannot be seen by the human eye. These waves can be used to detect heat (thermography) and are used in night vision equipment.

Ultraviolet Waves with frequencies slightly higher than violet are called ultraviolet and cannot be seen by the human eye. We cannot see these waves, but they can give us a sunburn!

ROY G BIV A way to remember the order of the colors in the visible spectrum, from lowest frequency to highest: red, orange, yellow, green, blue, indigo, violet.

Traveling Light – light can travel through any medium, including a vacuum!Medium A substance (or even a vacuum) that might let a wave pass through or might stop it from

passing throughTransmit or transmission When a wave travels through a medium

If light is transmitted, it goes throughAbsorb or absorption The stopping of light when it hits a wall or opaque objectReflect or reflection When light energy bounces off an object. Shiny objects reflect light.

Refraction When light hits an object that slows down its speed, it bends.

Transverse waves Light travels in transverse waves. These transverse waves can travel through many mediums, or through a vacuum.

Types of LightIncandescent An object is incandescent if it gives off heat and light.

Examples: fire, the sun, most light bulbs.Bioluminescent Living organisms that give off light.

Examples: fireflies, many deep sea organisms.Luminous An object is luminous if it gives off light without heat.

Examples: Fluorescent lights, glow sticks. Parts of a Wave

Crest or Peak The top of a waveTrough The bottom of a wave

Wavelength The distance from the one crest of a wave to the next. The wavelength of a wave determines its frequency

Frequency The number of waves per second, or the number of times the crest of a wave passes in a given amount of time. We see differences in frequency of the visible spectrum as differences in color.

Transmission of Light EnergyTransparent Objects that are transparent transmit all light waves so that we can easily see what is

on the other side. Examples: glass, water

Translucent Objects that are translucent transmit some light waves so that we we see some light pass through, and objects on the other side look blurry.

Examples: paper, lampshade, plasticOpaque Objects that are opaque do not transmit light and we can not see anything through

them. Examples: walls, doors, furniture, etc.

Lens A piece of clear material that bends, or refracts, light rays passing through it.

can be convex or concave

Prism A solid object that bends light; not a lens When white light enters a prism, the glass

bends the ray and splits up the colors of the visible spectrum.

Light travels in Transverse waves. Sound travels in longitudinal waves. AKA compression waves

Facts to Know about Sound

To have a sound, you need to have energy to produce vibrations, and matter, for the sound wave to travel through.

The matter that the sound waves travel through is sometimes called a medium. The energy can come from different movements, such as hitting, rubbing, blowing, or plucking.

Sound waves are produced by vibrating molecules.

Sounds differ because they have different wavelengths (frequency or pitch) and amplitudes (or volume).

Basics of Sound and Sound Waves

Wave A disturbance that travels (usually through a medium) from one location to another carrying

energy A sound wave is a series of rarefactions and compressions traveling through a substance

Acoustics The science of sound.

Amplitude & Volume(Sometimes called

Intensity)

How loud or quiet a sound is. The height of a sound wave from mid-point to the crest or trough. High amplitude = high volume/intensity = LOUD, because more energy was used to create

the sound wave. Low amplitude = low volume/intensity = quiet!, because less energy was used to create the

sound wave. Measured in units called decibels(dB). Volume is relative

Compression The part of a sound wave where molecules are pressed together tightly.

Compressional wave Another name for a sound wave.

Decibel (dB) The unit used to measure the strength/amplitude/volume of a sound. The quietest sound humans with normal hearing can hear is 0 decibels, and humans

experience pain when exposed to sounds above 160 decibels.

Doppler Effect The change in pitch of a sound when a passing object (like a car or airplane) changes from

high-pitch to low-pitch.

Frequency & Pitch

The number of sound waves per second, or the number of times the crest of a wave passes in a given amount of time. We hear differences in frequency as differences in pitch.

The unit used to measure the frequency of sound waves is the hertz. Higher notes have higher pitches/frequency. They also have shorter wavelengths. Example:

baby’s voice, flute. Lower notes have lower pitches/frequency. They also have longer wavelengths: Examples:

foghorn, bass. In music, frequency is called pitch. Different instruments have different pitches.

Medium The matter through which a wave travels. The medium can be solid, liquid or gas. Sound can NOT travel through a vacuum.

Rarefaction The part of a sound wave where molecules are loosely packed together.

Transmit When sounds travel or are sent through a medium

Wavelength The distance from the one crest of a wave to the next. The wavelength of the sound wave determines its frequency.

How People & Animals Use Sound

People and many animals use sound to speak or communicate with each other.

Echolocation When an animal uses sound reflections to find other animals.

Used by bats and dolphins, among other animals.

Hertz (Hz) The unit that frequency is measured in.

Normal human hearing range is 20-20,000 Hz.SONAR A device that uses sound waves to determine water depthThreshold The point where humans begin to detect and hear sounds.

Ultrasonic Sounds with a frequency above 20,000 hertz, that can not be heard by humans. Some animals, such as dogs, can hear ultrasonic sounds, like dog whistles. Ultrasound can be used to “see” inside the body.

Movement of Sound Waves – similar to light!When sound waves strike matter (or a medium), 3 different things can happen:

Transmission Sound waves pass through the matterAbsorption Sound waves are trapped by the matter

Reflection or Echno Sound waves hit a smooth, solid surface and are reflected by the surface. This is called an echo.

Sound waves travel through solids, liquids, and gases at different speeds.

Solids Sound waves travel fastest through solids since the molecules in a

solid are very tightly packed together.

Liquids Sound waves travel well through liquids, but not as quickly as they do

in solids.

Gases

Sound waves travel slowest through a gas since the molecules in a gas are packed together very loosely.

This is true even though most of the sounds we hear travel through air, a medium that is a gas.

! Diagrams of Sound Waves ! You should be able to identify the parts of the wave,

and the differences between the waves shown below.

Differences in the frequency of sound waves affect pitch.

Differences in the amplitude of sound waves affect volume.

Rarefaction Compression