Ch 02 Waves and Electromagnetic Radiation

Chapter 2: Waves and Electromagnetic Radiation

• Sections Covered:

  • 2.1 Longitudinal and Transverse Waves

  • 2.2 Measuring Waves

  • 2.3 The Electromagnetic Spectrum

2.1 Longitudinal and Transverse Waves

• Mechanical Waves:

  • Transmit energy through a medium without net transfer of matter.

  • Examples:

    • Waves on a string

    • Sound waves in air

• Electromagnetic Waves:

  • Can travel through empty space (not requiring a medium).

  • Example: Light.

• Transverse Waves:

  • Oscillations are perpendicular to the direction of wave energy (e.g., water waves, waves on a string).

• Longitudinal Waves:

  • Oscillations are parallel to the direction of wave energy (e.g., sound waves, compressions and rarefactions in a slinky).

• Wave Properties:

  • A wave may be:

    • A single pulse

    • Continuous or periodic (repeated crests/troughs or compressions/rarefactions).

  • Energy is transferred from one point to another with no net transfer of matter.

• Figure Representation:

  • Shows the movement of particles in longitudinal and transverse waves, illustrating compression and rarefaction.

2.2 Measuring Waves

• Wave Speed:

  • Can be measured using a rope example where changes in medium alter wave speed.

  • Formula:[ v = f \cdot \lambda ]Where:

    • ( v ): wave speed (m/s)

    • ( f ): frequency (Hz)

    • ( \lambda ): wavelength (m)

• Wave Parameters:

  • Amplitude (A): Maximum displacement from the average position.

  • Wavelength (( \lambda )): Distance between successive points in phase.

  • Phase (φ): State of the wave, with two particles in phase if they move in the same direction and have the same displacement.

  • Period (T): Time taken for one full cycle.

  • Frequency (f): Number of cycles per second (Hz).

• Graphs:

  • Displacement-distance and displacement-time graphs can visually represent wave properties.

2.3 The Electromagnetic Spectrum

• Nature of Light:

  • Described as a transverse electromagnetic wave needing no medium.

  • Composed of oscillating electric and magnetic fields.

• Wave Relationships:

  • Speed of electromagnetic waves: ( c \approx 3.0 \times 10^8 \ m/s ).

  • Formula:[ c = f \cdot \lambda ]

• The Electromagnetic Spectrum Breakdown:

  • Types of electromagnetic waves (ordered by wavelength and frequency):

    • Radio Waves

    • Microwaves

    • Infrared

    • Visible Light

    • Ultraviolet

    • X-rays

    • Gamma Rays

• Uses of Electromagnetic Radiation:

• Radio waves: For transmitting information over distances.

• Microwaves: Used in ovens (2.45 GHz frequency) to resonate with water molecules for heating.

• Infrared: Emitted by warm objects; used in night-vision goggles.

• Ultraviolet: Can cause skin damage; useful for scientific imaging.

• X-rays: Used for imaging, can damage cells with excessive exposure.

• Gamma Rays: Emitted from radioactive isotopes and astronomical sources.

Summary

• Key Takeaways:

  • Light is electromagnetic radiation; they are transverse waves with mutually oscillating electric and magnetic fields.

  • Electromagnetic waves do not require a medium and travel in a vacuum at high speeds.

  • Understanding the parameters and properties of waves allows for better comprehension of phenomena in physics.