Diffraction and Interference

1
Diffraction and Interference

• Laser Light
• Holograms
• Think and Explain

2
Incoherent Light

• Light emitted by a common lamp is incoherent. It
  has many phases of vibration as well as many
  frequencies.
• Incoherent light spreads out after a short
  distance and loses intensity.

3
Coherent Light

• A beam of light that has the same frequency,
  wavelength, phase, and direction is called
  coherent.
• There is no interference of waves within the beam
  and the beam will not spread out and diffuse.

4
Laser Light

• Laser light is coherent.
• LASER Light Amplification by Stimulated
  Emission of Radiation

5
The Laser

• In a laser, a light wave emitted from one atom
  stimulates the emission of light from a
  neighboring atom so that the crests of each wave
  coincide. Thus a coherent beam.

6
The Hologram

• The three-dimensional version of a photograph
  produced by interference patterns of laser beams.

7
The Hologram

• The interference of the laser beams produces
  fringe patterns on the photographic plate that
  record the depth of the surface of an object.

8
The Hologram

• The fringe pattern of a hologram diffracts light
  to produce wave fronts identical to the wave
  fronts given by the object.

9
The Hologram
So you see the 3-D image due to the way the
hologram diffracts light and the way this
diffracted light constructively and destructively
interfere. In this way, holograms are like
diffraction gratings.
10
The Hologram

• Every part of the hologram receives and records
  light from the entire object, so you can cut a
  hologram in half and still be able to view the
  whole image.

11
The Hologram

• You can magnify the image of a hologram by
  looking at it with light that has a longer
  wavelength than which it was made.

12
Think and Explain

• Page 498
• 1,2,7,10,11