soundwaves

A wave is energy moving from one place to another.

📦 Medium

• A medium is the material a wave travels through.

• Examples:
  

  • Sound → air, water, solids

  • Light → does NOT need a medium

🔊 Mechanical Waves (Sound)

• Require a medium to travel

• Example: sound waves

💡 Light Waves

• Do NOT require a medium

• Can travel through empty space

• Example: sunlight reaching Earth

🌈 Three Ways Light Interacts with Materials

1⃣ Reflection

Definition:

• When a wave bounces off a surface

Examples:

• Mirror

• Calm water

• Shiny metal (aluminum foil)

Key idea:

• Smooth surfaces reflect light clearly

2⃣ Absorption

Definition:

• When a material takes in a wave’s energy (often turns into heat)

Examples:

• Black clothing

• Dark surfaces

• Thick curtains (sound)

Key idea:

• Dark colors absorb more light

3⃣ Transmission

Definition:

• When a wave passes through a material

Examples:

• Clear glass

• Water

• Air (for sound)

Key idea:

• Transparent materials transmit light

• Material	What happens to light
  Mirror	Reflects most light
  Clear glass	Transmits most light
  Black shirt	Absorbs most light

🎨 Black vs White Surfaces

• Black objects: absorb most light → appear darker

• White objects: reflect most light → appear brighter

🌊 Sound Waves & Absorption

• Soft materials (curtains, carpet) absorb sound

• This makes rooms quieter

• Hard surfaces reflect sound

🪞 Why You Can See a Reflection but Not Behind a Mirror

• Light hits the mirror

• Light is reflected back to your eyes

• The mirror does not transmit light

• That’s why you can’t see through it

📝 Vocabulary You MUST Know

• Reflection – bouncing off

• Absorption – energy taken in

• Transmission – passing through

• Medium – material a wave travels through

• Light wave

• Mechanical wave

• A wave is a way that energy travels from one place to another without moving matter permanently.

  • Energy moves

  • Matter mostly stays in place

  • Waves can move through materials or empty space (depending on type)

  🔊 PART 1: SOUND WAVES

  🔊 What Is Sound?

  Sound is a type of mechanical wave created by vibrations.

  • Something must vibrate to make sound

  • Examples: vocal cords, speakers, guitar strings

  📦 Mechanical Waves

  A mechanical wave:

  • Requires a medium to travel

  • Cannot travel through empty space

  Examples:

  • Sound waves

  • Water waves

  • Seismic waves

  📦 Medium (Very Important)

  A medium is the material a wave travels through.

  Sound can travel through:

  • Air

  • Water

  • Solids

  🚫 Sound cannot travel through space (no air = no sound)

  🔁 How Sound Travels (Compression Waves)

  Sound travels as compressional (longitudinal) waves.

  Two parts:

  • Compression → particles are close together

  • Rarefaction → particles are spread apart

  Particles vibrate back and forth, but they do NOT move forward with the wave.

  🎚 Properties of Sound

  🔊 Volume (Loudness)

  • Depends on amplitude

  • Bigger vibrations = louder sound

  🎵 Pitch

  • Depends on frequency

  • Higher frequency = higher pitch

  • Lower frequency = lower pitch

  🧱 Sound Interactions

  1⃣ Reflection (Echo)

  • Sound bounces off hard surfaces

  • Example: echo in a gym

  2⃣ Absorption

  • Soft materials absorb sound

  • Examples: curtains, carpet, foam

  • Makes rooms quieter

  3⃣ Transmission

  • Sound passes through a medium

  • Example: hearing through a wall

  💡 PART 2: LIGHT WAVES

  💡 What Is Light?

  Light is a type of electromagnetic wave.

  • Does NOT require a medium

  • Can travel through empty space

  • Comes from energy sources (Sun, lamps)

  ⚡ Electromagnetic Waves

  Electromagnetic waves:

  • Travel as transverse waves

  • Can move through a vacuum (space)

  Examples:

  • Light

  • Radio waves

  • X-rays

  📈 How Light Travels

  Light travels in straight lines until it:

  • Reflects

  • Absorbs

  • Transmits

  • Refracts

  🌈 Light Interactions (MOST IMPORTANT)

  1⃣ Reflection

  Definition:

  Light bounces off a surface.

  Best reflectors:

  • Mirrors

  • Smooth, shiny surfaces

  Poor reflectors:

  • Rough surfaces (scatter light)

  2⃣ Absorption

  Definition:

  Light energy is taken in by a material and usually changed into heat.

  Examples:

  • Black clothing

  • Dark surfaces

  Key idea:

  • Dark colors absorb more light

  • Light colors absorb less

  3⃣ Transmission

  Definition:

  Light passes through a material.

  Materials that transmit light:

  • Clear glass

  • Water

  • Air

  4⃣ Refraction (extra but important)

  Definition:

  Light bends when it changes speed moving between materials.

  Example:

  • Straw looks bent in water

  Material Type	What light does
  Transparent	Transmits most light
  Translucent	Transmits some light (scatters)
  Opaque	Absorbs or reflects light

🎨 Color & Light

• White objects reflect most light

• Black objects absorb most light

• Objects appear colored because they reflect that color

🧪 REAL-WORLD EXAMPLES

• Thick curtains → absorb sound

• Aluminum foil → reflect light

• Black shirt in sun → absorbs light → gets warm

• Glass window → transmits light

📝 VOCABULARY YOU MUST MEMORIZE

• Wave

• Mechanical wave

• Light wave

• Medium

• Reflection

• Absorption

• Transmission

• Refraction

• Compression

• Rarefaction

• Amplitude

• Frequency

⭐ HOW TO ANSWER TEST QUESTIONS

If asked:

• Mirror? → reflection

• Dark object? → absorption

• Clear object? → transmission

• Sound? → needs medium

• Light? → no medium

🪞 Mirrors (Why You See Reflections)

• Mirrors reflect almost all incoming light

• Very little light is transmitted

• That’s why you can see images clearly

• That’s why you cannot see behind a mirror