Waves

Reading Warm-Up 1

• Objectives

  • Describe how waves transfer energy without transferring matter.

  • Distinguish between waves that require a medium and those that do not.

  • Explain the difference between transverse and longitudinal waves.

• Terms to Learn

  • wave

  • transverse wave

  • medium

  • longitudinal wave

• Discussion

  • Read the section silently and write down questions.

The Nature of Waves

• Definition of Waves

  • A wave is a disturbance that transmits energy through matter or empty space.

• Examples of Waves Observed at Home

  • Water waves (ocean), light waves (sun), microwaves (microwave oven), radio waves (radio), sound waves (phone call, voices).

• Commonality Among Waves

  • All waves carry energy away from their source without moving the material (medium) itself.

Wave Energy

• Energy can be carried away from its source by waves (e.g., splash of a rock in a pond).

• When waves travel, they do work on objects in their path (e.g., boats and ducks bobbing with waves).

Energy Transfer Through a Medium

• Medium

  • A substance through which a wave can travel; includes solids, liquids, and gases.

  • Mechanical waves require a medium (e.g., sound, ocean waves).

• Vibration of Particles

  • Waves transfer energy via the vibration of particles in the medium.

  • Example: A vibrating alarm clock inside a vacuum jar cannot be heard, showing sound requires a medium.

Types of Waves

• Mechanical Waves

  • Require a medium (e.g., sound, water waves).

• Electromagnetic Waves

  • Do not require a medium; can travel through a vacuum (e.g., light, microwaves).

Light Speed

• Light travels at approximately 300,000,000 m/s.

• Calculation Exercise

  • Find the distance light travels in one minute.

Transverse and Longitudinal Waves

• Transverse Waves

  • Particles move perpendicular to the direction of the wave (e.g., waves on a rope).

  • Crests (highest point) and troughs (lowest point) define transverse waves.

• Longitudinal Waves

  • Particles vibrate parallel to the wave's direction (e.g., sound waves).

  • Comprised of compressions (crowded particles) and rarefactions (spaced-out particles).

Wave Properties

• Amplitude

  • Maximum distance particles vibrate from their rest position; larger amplitude = more energy.

• Wavelength

  • Distance between two corresponding points (e.g., crest to crest).

• Frequency

  • Number of waves passing a point per second; measured in hertz (Hz).

  • Higher frequency = more energy.

Wave Equation

• Wave speed (v) = Wavelength (λ) × Frequency (f).

Wave Interactions

• Reflection

  • A wave bounces back after hitting a barrier (e.g., sound echo, light reflecting off surfaces).

• Refraction

  • Bending of a wave when moving from one medium to another (e.g., pencil in water appearing broken).

• Diffraction

  • Waves bend around barriers or openings (e.g., sound traveling around a corner).

• Interference

  • Occurs when two or more waves overlap:

    • Constructive Interference: Crests overlap crests, creating a larger wave.

    • Destructive Interference: Crest and trough overlap, reducing wave amplitude.

• Standing Waves

  • Formed by the interference of waves going in opposite directions; appear to be stationary.

• Resonance

  • Occurs when a vibrating object affects the vibration of another at a similar frequency.

Lab Activity: Wave Energy and Speed

• Question

  • Do larger disturbances create waves with more energy or speed compared to smaller disturbances?

• Hypothesis Testing

  • Experiment with different sizes of disturbances in water, measuring wave height (amplitude) and travel time.