Transcript Interference (8/4)

Chapter 35
{
© 2012 Pearson Education, Inc.
Interference
Constructive and destructive interference
Figure 35.2 at the right
shows two coherent
wave sources.
 Constructive interference
occurs when the path
difference is an integral
number of wavelengths.
 Destructive interference
occurs when the path
difference is a halfintegral number of
wavelengths.

© 2012 Pearson Education, Inc.
Q35.1
Two sources S1 and S2 oscillating in phase emit sinusoidal waves.
Point P is 7.3 wavelengths from source S1 and 4.3 wavelengths
from source S2. As a result, at point P there is
A. constructive interference.
B. destructive interference.
C. neither constructive nor destructive interference.
D. not enough information given to decide
© 2012 Pearson Education, Inc.
A35.1
Two sources S1 and S2 oscillating in phase emit sinusoidal waves.
Point P is 7.3 wavelengths from source S1 and 4.3 wavelengths
from source S2. As a result, at point P there is
A. constructive interference.
B. destructive interference.
C. neither constructive nor destructive interference.
D. not enough information given to decide
© 2012 Pearson Education, Inc.
Q35.2
Two sources S1 and S2 oscillating in phase emit sinusoidal waves.
Point P is 7.3 wavelengths from source S1 and 4.6 wavelengths
from source S2. As a result, at point P there is
A. constructive interference.
B. destructive interference.
C. neither constructive nor destructive interference.
D. not enough information given to decide
© 2012 Pearson Education, Inc.
A35.2
Two sources S1 and S2 oscillating in phase emit sinusoidal waves.
Point P is 7.3 wavelengths from source S1 and 4.6 wavelengths
from source S2. As a result, at point P there is
A. constructive interference.
B. destructive interference.
C. neither constructive nor destructive interference.
D. not enough information given to decide
© 2012 Pearson Education, Inc.
Two-source interference of light
• Figure 35.5 below shows Young’s double-slit experiment with
geometric analysis.
© 2012 Pearson Education, Inc.
Interference from two slits
• Follow the text discussion of
two-slit interference.
• Figure 35.6 at the right is a
photograph of the interference
fringes from a two-slit
experiment.
© 2012 Pearson Education, Inc.
Q35.3
In Young’s experiment, coherent light passing through
two slits (S1 and S2) produces a pattern of dark and
bright areas on a distant screen. If the wavelength of the
light is increased, how does the pattern change?
A. The bright areas move closer together.
B. The bright areas move farther apart.
C. The spacing between bright areas remains the
same, but the color changes.
D. any of the above, depending on circumstances
E. none of the above
© 2012 Pearson Education, Inc.
A35.3
In Young’s experiment, coherent light passing through
two slits (S1 and S2) produces a pattern of dark and
bright areas on a distant screen. If the wavelength of the
light is increased, how does the pattern change?
A. The bright areas move closer together.
B. The bright areas move farther apart.
C. The spacing between bright areas remains the
same, but the color changes.
D. any of the above, depending on circumstances
E. none of the above
© 2012 Pearson Education, Inc.
Q35.4
In Young’s experiment, coherent light passing through
two slits (S1 and S2) produces a pattern of dark and
bright areas on a distant screen.
What is the difference between the distance from S1 to
the m = +3 bright area and the distance from S2 to the
m = +3 bright area?
A. three wavelengths
B. three half-wavelengths
C. three quarter-wavelengths
D. not enough information given to decide
© 2012 Pearson Education, Inc.
A35.4
In Young’s experiment, coherent light passing through
two slits (S1 and S2) produces a pattern of dark and
bright areas on a distant screen.
What is the difference between the distance from S1 to
the m = +3 bright area and the distance from S2 to the
m = +3 bright area?
A. three wavelengths
B. three half-wavelengths
C. three quarter-wavelengths
D. not enough information given to decide
© 2012 Pearson Education, Inc.
Q35.5
Two radio antennas radiating
in phase are located at points
A and B, which are 6
wavelengths apart. A radio
receiver is moved along a
line from point B to point C.
A
6l
B
At what distance(s) from point B will the receiver
detect an intensity maximum?
A. 4.5l
B. 8l
C. 9l
D. both A. and B.
E. all of A., B., and C.
© 2012 Pearson Education, Inc.
C
A35.5
Two radio antennas radiating
in phase are located at points
A and B, which are 6
wavelengths apart. A radio
receiver is moved along a
line from point B to point C.
A
6l
B
At what distance(s) from point B will the receiver
detect an intensity maximum?
A. 4.5l
B. 8l
C. 9l
D. both A. and B.
E. all of A., B., and C.
© 2012 Pearson Education, Inc.
C
Interference in thin films
•
•
Figure 35.11 (right)
shows why thin-film
interference occurs,
with an illustration.
Figure 35.12 (below)
shows interference of
an air wedge.
© 2012 Pearson Education, Inc.