3 Chapter 4 Sound Light Sound q Sound

3 Chapter 4 Sound & Light

Sound q. Sound travels from one place to another as sound waves q. A sound wave is a longitudinal wave that can only travel through matter (Solids, liquids, gases) q. Vibrations produce sound waves by moving molecules in air.

How does the ear work? ¡ ¡ Sound waves are sent. The outer ear “catches the sound waves”. The middle ear takes the sound waves and “vibrates” the eardrum. The inner ear sends the messages to the brain. Middle Ear Outer Ear Sound Waves ¡ Inner Ear The brain puts it together and hooray! You hear your favorite song on the radio.

How sound waves travel! Outer ear – Middle ear – Inner ear – Catches Vibrates Sends sound Ear Message waves Drum To Brain

q Sound waves are made up of two parts: 1. Rarefactions 2. Compressions q The tuning fork causes molecules in the air to move closer and then farther apart

q Like other waves, a sound wave can be described by its: 1. Wavelength 2. Frequency q. Wavelength: distance from center of rarefaction to next rarefaction (vice versa) q. Frequency: The # of wavelengths that pass a given point in one second q. The unit for frequency is Hertz (Hz)

Speeds of Sound Waves q A sound wave’s speed increases when the material’s density increases. q. Solids and liquids are more dense than gases. q. Sound waves usually travel faster in solids than in liquids or gases. q. The speed of sound waves increase as the temperature increases.

If sound travels faster in water than in air…then why is it harder to talk to someone underwater? • Sound couples poorly moving from air to water. • Your lungs provide the burst of air when talking underwater. • In order for someone underwater to hear you, the sound waves have to go from the air in your mouth to the water surrounding you. • This causes the sound waves to get reflected where the air meets the water.

Pitch q Pitch: how high or low a sound seems q. A sound wave with a higher frequency has a higher pitch. q. A sound wave with a lower frequency has a lower pitch.

Loudness q. Loudness is the human sensation of how much energy a sound wave carries q. A shout carries more energy than a whisper. q. The energy that the wave carries relates to its amplitude.

Loudness (cont’d) q. The more energy a wave has the greater the amplitude. q. A decibel scale is one way to compare the loudness of sounds

Echo q. An echo is a reflected sound wave.

q. Some animals use echolocation to locate their prey and detect objects. q. Animals such as dolphins and bats send out sound waves and when those waves hit an object it bounces back vibrations.

Sound Travels Through Matter Liquids Gases Most of the sounds we hear travel through gases, such as air. Sound waves travel slowly through the air. For example: Sound from a bell, a horn, or an alarm clock travels through the air. Some sounds that we hear travel through water. Sound waves travel faster through water than through the air. Sonar is the way to use sounds to locate objects under water. Solids Some sounds that we hear travel through solids. Sound waves travel very fast through solids. For example: When you hit a drum, it vibrates, then the sound travels through the air, to your ears.

Ultrasound • Ultrasound scanners convert high-frequency sound waves to images of internal body parts. • The sound waves reflect from structures within the body. • The scanner analyzed the reflected waves and produces images called sonograms.

Breaking the Sound Barrier • When the vehicle (jet) exceeds the speed at which sound travels. • The cone of vapor you see is the existing moisture in the air being condensed by pressure wave created by the vehicle creating a cloud.

Lesson 2: Light

Light q. Light is a type of wave called an electromagnetic wave. q. Light does not need a medium to travel through. q. A medium is a material through which a wave travels. q. Light can travel through a vacuum. q. An example of a vacuum is the space between Earth and the Sun.

Light travels at different speeds through different mediums

Electromagnetic Spectrum q. The electromagnetic spectrum includes a range of electromagnetic waves. q. Wavelengths are measured in nanometers. Wavelength is 400 nm Wavelength is 700 nm

q. A light source is something that emits (gives off) heat. q. Examples of light sources include: burning candle, sun, light bulb q. A light ray is a narrow beam of light that travels in a straight line. Laser

q. A reflection is the process of light striking an object and bouncing off. We see things because they reflect light into our eyes. Homework

Depending on how materials interact with light, they are classified as: transparent, translucent, or opaque Transparent: almost all light passes through object Translucent: most light passes through & blurry image forms Opaque: no light passes through it

q. When light waves interact with matter they can be: 1. Transmitted light waves travel through a material (transparent object) 2. Absorbed light waves are converted to other forms; translucent object 3. Reflected light waves bounce of surface of material (opaque object)

Law of Reflection The angle of incidence is always equal to the angle of reflection. Normal Reflected ray Incident ray Angle of incidence Angle of reflection Mirror

HAVE YOU EVER SEEN DUST PARTICLES FLOATING IN THE AIR WHEN A BEAM OF SUNLIGHT SHINES THROUGH A WINDOW? q. This is an example of scattering. q. Scattering occurs when light waves travelling in one direction are made to travel in many directions.

Refraction q. Light waves change direction when they travel from one material to another. q. The bending of a wave as it moves from one material to another is called refraction. q. This is due to a change in speed.

Light q. Light is slower when passing through dense materials.

Retina Rods • 120 million • Allow you to see in dim light • Black and white signals – does not allow you to see color. Cones • 6 million • Response to light waves with different wavelengths allow you to see different colors. • 3 types – each detecting a different wavelength. • In some people, not all 3 function properly = color blindness/color deficiency.

People with color deficiency cannot see a number in this picture!

How your eye works

LESSON 3: MIRRORS & LENSES

Regular Reflection Light waves reflect off a mirrorlike surface. The smooth surface reflects light rays traveling in the same direction at the same angle.

Diffuse Reflection When a surface is not smooth the reflected angle travels in many different directions.

Mirrors A mirror is any reflecting surface that form an image by regular reflection. Plane Mirror: u Flat surface u Same image, just reversed left to right Convex Mirror: Concave Mirror: u Curved outward u Curved Inward u Objects can appear u Objects are smaller upside down or right and right-side up

Cosmetic mirrors are often concave mirrors. Image becomes magnified. Convex mirrors are often used for safety purposes.

Lens A lens is a transparent object with at least one curved side that causes light to change direction Convex Lenses • Curved outward • Thicker in the middle • Objects appear larger

Concave Lens • Curved inward • Thicker at the sides • Object is shown smaller Glasses for nearsightedness (can’t see far)

How do objects get their color? Objects reflect light. Colors depend on the wavelengths of the light waves it reflects. The rose looks red because all the other wavelengths are absorbed but red is reflected.

White light is a combination of all light waves. Neon lights emit (give off) different colors. The appearance of an object changes under different lights.