1. Interference and Diffraction.
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Interference and Diffraction.
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2. Light - what is it? Particles or Waves?
200 year debate started in 1700’s.
Supposedly settled in 1802.
Finally resolved in early 1900’s.
Before the 1700’s!
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3. Jean-Baptiste Biot (1774-1862)
The Particle Theorists
Pierre Simon Laplace
( )
Sir Isaac Newton
( )
Support later provided by:
Jean-Baptiste Biot ( )
Sir David Brewster ( )
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4. The Wave Theorists Support later provided by: Thomas Young (1773-1829)
Rene DesCartes Christian Huygens Robert Hooke
( ) ( ) ( )
Support later provided by:
Thomas Young ( )
Max Planck ( )
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5. Speed of Light Speed in Vacuum Speed in Other Materials 300,000 km/sec
186,000 mi/sec
Speed in Other Materials
Slower in Air, Water, Glass
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6. The Electromagnetic Spectrum A range of light waves extending in wavelength from radio waves to gamma rays.
Radio Waves - communication
Microwaves - used to cook
Infrared - heat
Visible Light - detected by your eyes
Ultraviolet - causes sunburn
X-rays - penetrates tissue
Gamma Rays - most energetic
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7. The Visible Spectrum
A range of light waves extending in wavelength from about 400 to 700 nanometers.

8. Electromagnetic Spectrum
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9. Francesco Grimaldi ( ), Italian mathematician, physicist, and artist, first noticed interference fringes looking at the shadow of an opaque object.
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10. LNK2LRN
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11. How light Diffracts and Interferes with itself as it passes through 2 narrow openings.
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12. Thomas Young demonstrated diffraction and interference of light in 1802.
Is this an example of chromatic aberration?
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And remember, “Blue bends best!”
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13. LNK2LRN
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14. LNK2LRN λ = x·d / L or λ = d·sinθn / n
How to derive the equation for λ , the wavelength of light. x λ
λ = x·d / L or λ = d·sinθn / n
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15. Violet 410-440 Blue 440-490 Green 490-540 Yellow 540-600
Correlation of spectrum color with wavelength (nanometers).
Color Wavelength (nm)
Violet
Blue
Green
Yellow
Orange
Red
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16. X-ray diffraction allows us to see the molecular lattice in a crystal.
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17. The arrangement of atoms in a crystal.
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18. THE END.
Next Topic: Electric Forces and Fields.
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