A repeating disturbance that carries energy from one place to another without transporting matter the whole distance.

The size of a wave; for transverse waves, the height from rest to crest. Larger amplitude means more energy.

The distance between two matching points on a wave, such as crest to crest or compression to compression.

The number of wave cycles that pass a point each second, measured in hertz (Hz).

A wave that requires a medium (solid, liquid, or gas) to travel, such as sound or water waves.

A repeating disturbance that carries energy from one place to another without transporting matter the whole distance.

How high or low a sound seems to your ears; depends on the frequency of the sound wave.

How strong or intense a sound seems; related to the amplitude and energy of the sound wave.

The size of a wave; for transverse waves, the height from rest to crest. Larger amplitude means more energy.

Waves, Sound, and Light — SHS Science Foundations: Integrated Chemistry, Biology, and Physics

1. What Is a Wave?

What is a Wave?

A wave is a repeating disturbance that carries energy from one place to another without moving matter the whole distance. Like a stadium "wave": people move up and down, but the wave shape travels around.

Waves and Vibrations

Waves are usually caused by vibrations. A vibration is a back-and-forth or up-and-down motion. The vibration starts locally, but the energy spreads out as a wave.

Two Types of Wave Motion

Transverse waves: medium moves at right angles to the wave direction (like ripples on a rope). Longitudinal waves: medium moves back and forth in the same direction as the wave (like sound in air).

Link to Forces and Energy

A force can start a vibration. That vibration sends out a wave that carries energy through a material or through space, connecting to what you learned about forces and energy transfer.

2. Wave Basics: Amplitude, Wavelength, Frequency, Speed

Amplitude

Amplitude tells how "big" the wave is. For transverse waves, it is the height from the rest position to a crest. Larger amplitude means the wave carries more energy.

Wavelength

Wavelength (λ) is the distance from one point on a wave to the next matching point (crest to crest). Short wavelength means crests are packed close together.

Frequency

Frequency (f) is how many wave cycles pass a point each second. It is measured in hertz (Hz). Higher frequency means more cycles per second.

Wave Speed

Wave speed (v) is how fast the wave pattern moves through the medium. It depends on the medium and the wave type. The key link is `v = f × λ` (no calculations needed now).

Changing f and λ

If wave speed in a medium is fixed, then higher frequency means shorter wavelength, and lower frequency means longer wavelength. You will use this to explain pitch and color.

3. Mechanical vs Electromagnetic Waves

Mechanical Waves

Mechanical waves need a material medium (solid, liquid, or gas). Examples: sound in air, water waves, seismic waves. They cannot travel through the vacuum of outer space.

Electromagnetic Waves

Electromagnetic (EM) waves do not need a medium. They are vibrations of electric and magnetic fields and can travel through empty space, like sunlight reaching Earth.

EM Wave Examples

Examples of EM waves: radio and TV signals, microwaves (including Wi‑Fi), visible light, infrared, ultraviolet, X‑rays, and gamma rays. All move at the speed of light in vacuum.

Everyday Comparison

Astronauts’ voices are sound (mechanical) but radios convert them to radio waves (EM). Radio waves cross space; sound alone cannot travel through vacuum.

Energy and Information

Both wave types carry energy and information. Your voice uses sound waves in air. Your phone and Wi‑Fi use electromagnetic waves to send data.

4. Real-World Wave Examples

Speakers and Sound

A speaker cone vibrates back and forth, creating compressions and rarefactions in air. These are longitudinal mechanical waves. Amplitude controls loudness; frequency controls pitch.

Phones and Radio Waves

Your phone turns voice or data into radio waves (electromagnetic). These waves travel through air and space to towers or satellites, carrying information without needing a material medium.

Ocean Waves

In ocean waves, water particles mostly move in small circles. The wave shape moves; the water does not travel far. Larger amplitude waves carry more energy and hit the shore harder.

Microwave Ovens

Microwave ovens use microwave radiation (EM waves) to make water molecules in food vibrate faster, increasing thermal energy and heating the food.

Common Pattern

In all these examples, a vibration sends out a wave that carries energy or information from one place to another.

5. Sound: Production, Travel, Pitch, and Loudness

Sound as a Wave

Sound is a mechanical longitudinal wave. It needs a medium like air, water, or solids. Vibrating objects create regions of compression and rarefaction in the medium.

How Sound Travels

Sound travels fastest in solids, slower in liquids, and slowest in gases, because particles are closest in solids. In a vacuum there is no medium, so no sound can travel.

Pitch and Frequency

Pitch is how high or low a sound seems. It depends on frequency. High frequency waves sound high-pitched; low frequency waves sound low-pitched.

Loudness and Amplitude

Loudness relates to amplitude. Larger amplitude sound waves carry more energy and sound louder. Very loud sounds (large amplitude) can damage hearing.

How We Hear

Sound waves vibrate the eardrum, then tiny bones and fluid in the inner ear. Hair cells convert these vibrations into electrical signals that the brain interprets as sound.

6. Sound Thought Experiments

Use these quick thought exercises to apply what you know about sound.

Silent Space Movie

Imagine a spaceship explodes in deep space, far from any planet.

In real life, would you hear a "boom" from a nearby ship with the windows closed?
Answer in your own words: Why or why not, using the idea of mechanical waves and medium?

Guitar String Challenge

You tighten one guitar string and pluck it. Compared to the same string when it was looser:

Does the frequency of the vibration increase or decrease?
Does the pitch go up or down?

Write a one-sentence explanation connecting frequency and pitch.

Library vs Concert

You whisper in a library and shout at a concert.

Which has the larger amplitude of sound waves?
Which has more energy in the wave?

Explain how amplitude, loudness, and energy are connected.

Solid Wall Trick

You put your ear to a solid wall while someone taps on the other side.

Why can you sometimes hear the tapping better through the wall than through the air?

Use what you know about sound speed in different media.

7. Light as an Electromagnetic Wave

Light as EM Wave

Light is an electromagnetic wave, a vibration of electric and magnetic fields. EM waves, including light, can travel through a vacuum at the speed of light (~300,000 km/s).

Visible Spectrum

Visible light is the part of the EM spectrum our eyes detect. Different wavelengths/frequencies correspond to colors: red is longer wavelength, violet is shorter wavelength.

White Light and Color

White light is a mixture of many wavelengths. An object’s color depends on which wavelengths it reflects and which it absorbs.

Examples of Color

A red shirt reflects mainly red light and absorbs others. A black object absorbs most visible light and often feels warmer in sunlight because it converts more light to heat.

Light vs Sound

Light is electromagnetic and can cross space; sound is mechanical and needs a medium. Light travels much faster than sound, so you see lightning before hearing thunder.

8. Reflection and Refraction (Mirrors, Lenses, and Bending Light)

Reflection

Reflection is when light bounces off a surface. Smooth surfaces like mirrors reflect light in an orderly way, giving clear images. Rough surfaces scatter light, so images look blurred or not visible.

Refraction

Refraction is the bending of light when it passes from one medium to another, like air to water. Light changes speed in different materials, and this speed change causes the ray to bend.

Refraction Example

A straw in a glass of water looks bent at the surface because light from the straw refracts as it moves from water to air, changing direction before reaching your eyes.

Lenses

Lenses use refraction. Converging (convex) lenses bend light inward to focus it. Diverging (concave) lenses spread light outward. They are used in glasses, cameras, and microscopes.

Mirrors and Fiber Optics

Mirrors form images by reflection. Fiber optic cables guide light by repeated internal reflection, allowing light signals to travel long distances for internet and medical imaging.

9. Quick Check: Waves, Sound, and Light

Answer this question to check your understanding of wave types and properties.

Which statement is MOST accurate?

Sound and light are both mechanical waves and cannot travel through a vacuum.
Sound is a mechanical wave that needs a medium; light is an electromagnetic wave that can travel through a vacuum.
Sound is an electromagnetic wave; light is a mechanical wave.
Both sound and light require solids to travel; they cannot move through gases.

Show Answer

Answer: B) Sound is a mechanical wave that needs a medium; light is an electromagnetic wave that can travel through a vacuum.

Sound is a **mechanical** longitudinal wave and must have a medium like air, water, or solids. Light is an **electromagnetic** wave and can travel through a vacuum, such as from the Sun to Earth.

10. Key Term Review

Flip through these flashcards to review the main ideas from this module.

Wave: A repeating disturbance that carries energy from one place to another without transporting matter the whole distance.
Amplitude: The size of a wave; for transverse waves, the height from rest to crest. Larger amplitude means more energy.
Wavelength (λ): The distance between two matching points on a wave, such as crest to crest or compression to compression.
Frequency (f): The number of wave cycles that pass a point each second, measured in hertz (Hz).
Mechanical wave: A wave that requires a medium (solid, liquid, or gas) to travel, such as sound or water waves.
Electromagnetic wave: A wave of vibrating electric and magnetic fields that can travel through a vacuum, such as light or radio waves.
Pitch: How high or low a sound seems; depends on the frequency of the sound wave.
Loudness: How strong or intense a sound seems; related to the amplitude of the sound wave.
Reflection: The bouncing of a wave off a surface, such as light off a mirror or sound creating an echo.
Refraction: The bending of a wave as it passes from one medium to another and changes speed, such as light from air into water.
Visible spectrum: The range of electromagnetic wavelengths that human eyes can detect, appearing as colors from red to violet.
Fiber optics: Thin glass or plastic fibers that guide light signals, using internal reflection to carry data over long distances.

Key Terms

wave: A repeating disturbance that carries energy from one place to another without transporting matter the whole distance.
pitch: How high or low a sound seems to your ears; depends on the frequency of the sound wave.
loudness: How strong or intense a sound seems; related to the amplitude and energy of the sound wave.
amplitude: The size of a wave; for transverse waves, the height from rest to crest. Larger amplitude means more energy.
frequency: The number of wave cycles that pass a point each second, measured in hertz (Hz).
reflection: The bouncing of a wave off a surface, such as light off a mirror or sound producing an echo.
refraction: The bending of a wave when it passes from one medium to another and changes speed, such as light entering water from air.
wave speed: How fast the wave pattern moves through a medium or space; for many waves, linked to frequency and wavelength by v = f × λ.
wavelength: The distance between two matching points on a wave, such as crest to crest or compression to compression.
fiber optics: Technology that uses thin glass or plastic fibers to guide light signals, mainly for communication and medical imaging.
mechanical wave: A wave that needs a material medium (solid, liquid, or gas) to travel, such as sound or water waves.
transverse wave: A wave in which the medium moves at right angles to the direction the wave travels, like waves on a rope.
visible spectrum: The range of electromagnetic wavelengths that human eyes can detect, perceived as colors from red to violet.
longitudinal wave: A wave in which the medium vibrates back and forth in the same direction that the wave travels, like sound in air.
electromagnetic wave: A wave of vibrating electric and magnetic fields that can travel through a vacuum, including light, radio waves, and X‑rays.