IB MYP 4-5 Physics- Mechanical waves vs electromagnetic waves- Study Notes - New Syllabus
IB MYP 4-5 Physics-Mechanical waves vs electromagnetic waves- Study Notes
Key Concepts
- Mechanical waves vs electromagnetic waves
Mechanical Waves vs Electromagnetic Waves
Mechanical Waves vs Electromagnetic Waves
- Mechanical Waves: Waves that require a medium (solid, liquid, or gas) for their propagation. They transfer energy by particle vibrations.
- Electromagnetic (EM) Waves: Waves that do not require a medium. They consist of oscillating electric and magnetic fields, perpendicular to each other and to the direction of wave propagation.
1. Mechanical Waves
- Need a medium to travel (cannot move in vacuum).
- Formed by oscillations of particles in the medium.
- Can be longitudinal (sound waves) or transverse (water waves, seismic S-waves).
- Examples: Sound waves, water waves, seismic waves.
2. Electromagnetic Waves
- Do not need a medium (can travel in vacuum).
- Consist of mutually perpendicular oscillating electric and magnetic fields.
- Always transverse in nature.
- Examples: Light, radio waves, X-rays, gamma rays.
Mechanical vs Electromagnetic Waves
| Feature | Mechanical Waves | Electromagnetic Waves |
|---|---|---|
| Medium requirement | Require a medium | Do not require a medium |
| Nature of wave | Longitudinal or Transverse | Always Transverse |
| Propagation speed | Depends on medium (e.g. sound: ~343 m/s in air) | Constant in vacuum (\(3 \times 10^8 \, \text{m/s}\)) |
| Examples | Sound, water waves, seismic waves | Light, radio waves, X-rays |
Example:
Can sound travel in space (vacuum)? Why or why not?
▶️ Answer/Explanation
Sound is a mechanical wave and requires air (or another medium) for propagation.
In vacuum, there are no particles to transmit vibrations.
Final Answer: \(\boxed{\text{No, sound cannot travel in vacuum.}}\)
Example:
Why can we see sunlight from the Sun even though space is a vacuum?
▶️ Answer/Explanation
Sunlight is an electromagnetic wave.
Electromagnetic waves do not need a medium and can propagate through the vacuum of space.
Final Answer: \(\boxed{\text{Because light is an EM wave and travels in vacuum.}}\)
Example:
The speed of sound in air is \(343 \, \text{m/s}\). The speed of light in vacuum is \(3 \times 10^8 \, \text{m/s}\). How many times faster is light than sound?
▶️ Answer/Explanation
\(\dfrac{3 \times 10^8}{343} \approx 8.75 \times 10^5\)
So, light is nearly a million times faster than sound.
Final Answer: \(\boxed{\text{Light is about \(8.75 \times 10^5\) times faster than sound.}}\)