Chapter 37
Wave Optics
EXAMPLES
Chapter 37:
Interference of Light Waves: Examples
Example 37.1 Wavelength of a Light Source
A viewing screen is separated from a double-slit source by 1.2 between
slits is 0.030 mm. The second order bright fringe (m = 2) is 4.5 cm from
the center line.
Determine the wavelength of the light.
ybright  m

L
dybright
mL
d

 
dybright

mL
 3 105 m  4.5 102 m 
2 1.2m 
 5.6 107 m  560nm
Calculate the distance between adjacent bright fringes
ym 1  ym   m  1
L
m
L

L

d
d
d
5.6 107 m  1.2m 

ym 1  ym 
 2.2cm
3 105 m
Example 37.2 Fringes of Two Wavelengths
A light source emits visible light of two wavelengths:  = 430 nm
and ’ = 510 nm. The source is used in a double-slit interference
experiment in which L = 1.50 m and d = 0.025 mm. Find the
separation between the third-order bright fringes.
430 10 m  1.5m 

L
L
m
3
3
 7.7cm
9
ybright
0.025  103 m
9
510

10
m  1.5m 

 'L
 'L
y 'bright  m
3
ym 
 9.2cm 
3
d
d
0.025 10 m
y  y 'bright  ybright  1.5cm
d
d
Example 37.3 Six slits (Quiz 37.2)
Sketch the interference patter from six slits
 The number of secondary maxima is always
N – 2 where N is the number of slits
 Because N = 6, the secondary maxima are 1/36 as intense
as the primary maxima.
Material for the 2nd Midterm
Material from the book to Study!!!
Objective Questions: 3-6
Conceptual Questions: 1-3
Problems: 4-9-11-16-19-21-23