Multiple-Slit Interference

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Multiple-Slit Interference
Uniform slits, distance d apart. Light of
wavelength l. Screen L away
Thin slits ? compared to d)
L gtgt d then path length difference between
ADJACENT SLITS
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Multiple-Slit Interference Maxima
For MAXIMUM amplitude of combined waves (totally
constructive interference), need
Locations of maxima Evenly spaced.
Correct for multiple (N gt 1) slits
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Multiple-Slit Interference Minima
More difficult need to consider of
slits/sources
2 slits
3 slits Try
get
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N 2 d 0.1 mm l 700 nm
N 3 d 0.1 mm l 700 nm
N 4 d 0.1 mm l 700 nm
N 5 d 0.1 mm l 700 nm
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N 2 d 0.1 mm l 700 nm
N 3 d 0.1 mm l 700 nm
N 4 d 0.1 mm l 700 nm
N 5 d 0.1 mm l 700 nm
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(No Transcript)
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ConcepTest 61 Consider the interference
pattern of four (thin) slits equally spaced a
distance d apart
Consider the following choices
1. 0 4. 3p/2
2. p/2 5. 2p
3. p 6. none of the above
a) What is the phase difference between adjacent
slits for the CENTRAL MAXIMUM? b) What is the
phase difference between adjacent slits for the
FIRST SIDE MINIMUM? c) What is the phase
difference between adjacent slits for the SECOND
SIDE MINIMUM? d) What is the phase difference
between adjacent slits for the THIRD SIDE
MINIMUM?
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N 5 d 0.1 mm l 700 nm
N 5 d 0.09 mm l 700 nm
N 5 d 0.08 mm l 700 nm
N 5 d 0.07 mm l 700 nm
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Diffraction Grating

• Multiple Slit Interference
• LOTS of Slits
• VERY CLOSELY spaced

• Example
• Diffraction Grating from lab
• Laser Vision Glasses
• CD (reflection grating details next week)

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ConcepTest 62 You look at a bright source of
white light through a diffraction grating.
Looking away from the center, you will see
colors. What color will you see closest to the
center?
1. Red 4. Green
2. Orange 5. Blue
3. Yellow 6. Violet
Brainstorm What will you see at the center?
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N 5 d 0.1 mm l 700 nm
N 5 d 0.1 mm l 600 nm
N 5 d 0.1 mm l 500 nm
N 5 d 0.1 mm l 400 nm