# Chapter 14 Sound and Light Energy

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Chapter 14 Sound and Light Energy

Lesson 1: What is sound energy?
Sound energy is a form of energy that travels in waves. Sound can travel through solids, liquids, and gases.

How is the sound made? Sound is actually created by objects vibrating. A vibration is a kind of wiggle; a quick back-and-forth movement.

How the vibration works!
Think about a guitar: When you pluck a string, the string vibrates. When it vibrates energy is passed into the air causing the air to vibrate as well. The vibrations travel through the air as sound waves. A sound wave is a disturbance that moves energy through matter.

Sound Waves There are 2 types of sound waves:
Transverse (sound travels up and down) Longitudinal (sound that travels left to right)

Frequency The number of waves that pass a point in a certain length of time. How frequently does the sound wave happen?

Wavelength The distance between one point on a wave and another point on a different wave.

How does sound travel? Sound waves compress the particles in whatever kind of matter it is traveling in. It can travel in solids, liquids, and gases. Sound travels at different speeds through different kinds of matter.

Why do sounds travel at different speeds?
There are 2 main causes that affect how fast the sound travels through the medium. How much do the particles move in response to the vibration and how easily they move back to their original position? How strongly are the particles attached or attracted to one another?

Solids, Liquids, and Gases
Sound moves very quickly through a solid. Sound moves a little slower through water. Sound moves slowest through gases.

Echoes An echo is a reflected sound. When a sound is traveling it sometimes bumps into objects. Think about being in a cave- if you yelled your name in a cave, you would hear your name echo because of the walls that surround you.

Lesson 2 How is sound made?

Frequency, Wavelength, and Pitch

Frequency Frequency is how often the sound wave occurs in a given amount of time.

Wavelength Wavelength is the length from one top of a sound wave to the next top of sound wave.

Pitch It is what makes a sound seem low or high. It depends on a sound frequency. If an object vibrates slowly, the pitch is low and the frequency is low. If an object vibrates quickly, the pitch is high and the frequency is high.

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Lesson 3 What is light energy?

Light is a form of energy, that travels in waves.
What is light? Light is a form of energy, that travels in waves.

How does light travel? Light travels in waves known as transverse waves. Light travels in a straight line called a ray. A ray fans outward from the source of light.

Sources of light The most important source of light is the Sun. Some animals give off light called “bioluminescence” which is created because of a chemical reaction in the animal’s body.

A shadow is created when an object blocks light.

Electromagnetic Spectrum
Scientists refer to all forms of light energy as electromagnetic radiation. The human eye can only see the wavelengths and the frequencies in the visible spectrum.

Electromagnetic Spectrum Continued
As you move from left to right on the spectrum, wavelength decreases and frequency increases.

So, red light has the longest wavelength and lowest frequency, and violet light has the shortest wavelength and highest frequency.

Light Waves We Can’t See
Ultraviolet waves, x-rays, and gamma rays are high-energy wave. The are invisible to the human eye because their waves are too short.

Did You Know This? All electromagnetic waves travel at the same speed through empty space and they are carry energy. It is harmful for humans to absorb the high-energy waves.

How do light and matter interact?
Lesson 4 How do light and matter interact?

Matter is any object that has mass.
What is matter? Matter is any object that has mass.

Light and Matter Together
Light waves travel in a straight line until an object gets it the way. Then 3 different things can happen: Light waves can reflect off the object Light waves can pass through the object Light waves can be absorbed by the object.

Reflection Reflection occurs when light rays bounce, or reflect, from a surface back to our eyes.

Absorption Absorption takes place when an object takes in all the light waves. Once this happens the light turns into heat energy.

What we actually see When light hits an object, whatever colors the object reflects is the color we see the object as. The reason an object looks white, is because it reflects all colors.

Letting Light Through Materials can be grouped
into 3 categories based off of how much light they let through. Transparent Translucent Opaque

Transparent If a material is transparent, that means light rays can pass through them.

Translucent If a material is translucent, that means it lets some light rays through it.

If a material is opaque, that means NO light rays pass through it.

Light Traveling Light travels differently through different mediums. Light travels slowly through gases, it travels slower through a liquid, and it travels slowest through a solid.

Refraction When light travels from one medium to another, it can bend or “refract”. The change in speed is what causes the bending.

Lens Lenses are curved pieces of clear glass or plastic that refract light that passes through them. There are 2 main types of lenses: convex and concave.

Convex Lenses This type of lens is thicker in the middle than at the edges. It is shaped somewhat like a football.

Convex Lens Continued When light rays pass through a convex lens the light rays bend in toward the middle of the lens. A convex lens can magnify an object, making them look larger. An example of a convex lens would be a magnifying glass or a microscope.

Concave Lens This types of lens is thinner in the middle than at the edges. It is shaped an hour glass.

Concave Lens Continued
When light passes through a concave lens, the light rays bend out toward the thicker edges of the lens. When looking through concave lens, the light rays spread apart, so the object seems smaller than it is. Many telescopes have this kind of lens.