# 3 Chapter 4 Sound & Light.

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3 Chapter 4 Sound & Light

Sound Sound travels from one place to another as sound waves
A sound wave is a longitudinal wave that can only travel through matter (Solids, liquids, gases) 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 – Catches sound waves Middle ear –
Vibrates Ear Drum Inner ear – Sends Message To Brain

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

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

Speeds of Sound Waves A sound wave’s speed increases when
the material’s density increases. Solids and liquids are dense than gases. more Sound waves usually travel faster in solids than in or liquids gases. 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 Pitch: how high or low a sound seems
A sound wave with a higher frequency has a pitch. higher A sound wave with a lower frequency has a pitch. lower

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

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

Echo An echo is a reflected sound wave.

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

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

Light travels at different speeds through different mediums

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

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

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

Transparent: almost all light passes through object
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

When light waves interact with matter they can be:
Transmitted 2. Absorbed 3. Reflected light waves travel through a material (transparent object) light waves are converted to other forms; translucent object 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 Incident ray Reflected ray Angle of incidence Angle of reflection Mirror

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

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

Light Light is slower when passing through dense materials.

Retina Cones Rods 6 million 120 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. Rods 120 million Allow you to see in dim light Black and white signals – does not allow you to see color.

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

LESSON 3: MIRRORS & LENSES

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

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

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

Glasses for nearsightedness (can’t see far)
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 light. Colors depend on the of the light waves it reflects. reflect wavelengths The rose looks red because all the other wavelengths are absorbed but red is reflected.

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

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