Waves

1
Waves Electromagnetic Radiation

• Chapter 6

Great Idea Whenever an electrically charged
object is accelerated, it produces
electromagnetic radiationwaves 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 (?)
• 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, EM 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 (EM) waves are propagations of
  coupled electric field and magnetic field.
• EM waves are transverse wave.
• All EM 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 EM 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 EM Waves

12
Other EM 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)