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Waves & Electromagnetic Radiation

Waves & Electromagnetic Radiation. Chapter 6. Great Idea : Whenever an electrically charged object is accelerated, it produces electromagnetic radiation—waves of energy that travel at the speed of light. The Nature of Waves. Wave A traveling disturbance Examples: slinky, water, rope, etc

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Waves & Electromagnetic Radiation

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  1. Waves & Electromagnetic Radiation Chapter 6 Great Idea: Whenever an electrically charged object is accelerated, it produces electromagnetic radiation—waves of energy that travel at the speed of light

  2. The Nature of Waves • Wave • A traveling disturbance • Examples: slinky, water, rope, etc Energy is transferred by waves but not the medium. • Properties of Waves (physical quantities) • Wavelength (λ) • Frequency (f) • Period (T) • Velocity (v) • Amplitude (A) Units of above quantities

  3. Relationship of Wave Properties • Velocity of a wave • Equation: Example 6-1 On a relative calm day at the beach, ocean waves traveling 2 meters per second hit the shore every 5 seconds. What is the wave length of these ocean waves?

  4. Two Kinds of Waves • Transverse • Motion is perpendicular to wave direction • Examples: water wave, E&M wave • Longitudinal • Motion is along the wave direction • Examples: sound wave

  5. The Sound of Music Standing waves on a guitar string with fixed end on both sides. Organ pipes with ends open Example 6-2 The human ear can hear sounds at frequencies from 20 Hz to 20,000 Hz. What are the longest and shortest wavelengths you can hear? What is the longest or shortest organ pipes you are likely to see?

  6. Interference • What will happen if two waves meet? • Interference • Constructive Interference • Act together • Destructive Interference • Cancellation

  7. The Electromagnetic Wave Electromagnetic (E&M) waves are propagations of coupled electric field and magnetic field. • E&M waves are transverse wave. • All E&M waves have the same speed, the speed of light

  8. Doppler Effect Wave motion is independent of its source If source moves, frequency appears to change to receivers

  9. Transmission, Absorption, and Scattering • Transmission • Wave passes through matter • Refraction: wave change direction at the interface of two different medium. • Absorption • Wave and its energy are absorbed (changed into heat) • Scattering • Waves absorbed and reemitted • Diffuse scattering • Reflection

  10. Visible Light and the Electromagnetic Spectrum Visible light is part of the entire E&M Wave spectrum (400nm -700 nm) • Higher frequency (blue) with higher energy • Lower frequency (red) with lower energy Human eyes’ sensitivity to colors

  11. AM and FM Radio Transmission • Radio Waves • Frequency Range: kHz to hundreds of mHz • Longest wavelength for E&M Waves

  12. Other E&M Waves and Their Applications Infrared Radiation (1 micron to 1mm) Microwave (1 mm-1m) Ultraviolet (100nm-400 nm) X-Ray (0.1 nm-100nm) Gamma Rays (0.001nm-0.01nm)

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