# Chapter 21 Huygen Principle and interference¶

## Example 21.1 Page no 1090¶

In [6]:
#Goven
d=5*10**-3                             #m
D=1.0                                   #m
b=0.1092*10**-3

#Calculation
l=(d*b)/D

#Result
print"Wavelength of light used is", l*10**10,"A"

Wavelength of light used is 5460.0 A


## Example 21.2 Page no 1090¶

In [13]:
#Given
l=6200*10**-10                   #m
D=0.8
b=2.8*10**-3/4.0

#Calculation
d=(l*D)/b

#Result
print"Separation of the two slit is", round(d*10**3,1),"mm"

Separation of the two slit is 0.7 mm


## Example 21.3 Page no 1090¶

In [16]:
#Given
a=62
l=5893
l1=4358.0

#Calculation
n=(a*l)/l1

#Result
print"Fringes required is", round(n,0)

Fringes required is 84.0


## Example 21.4 Page no 1091¶

In [25]:
#Given
l=6000*10**-10                       #m
D=0.800                               #m
d=0.200*10**-3                         #m

#Calculation
x2=(3*l*D)/(2.0*d)
x21=(2*D*l)/d

#Result
print"(i) Distance of the second dark fringe is", x2*10**2,"cm"
print"(ii) Distance of the second dark fringe is", x21*10**2,"cm"

(i) Distance of the second dark fringe is 0.36 cm
(ii) Distance of the second dark fringe is 0.48 cm


## Example 21.6 Page no 1091¶

In [29]:
#Given
Imax=16
Imin=4

#Calculation
r=Imax/Imin

#Result
print"Deduce the ratio of intensity is", r,":1"

Deduce the ratio of intensity is 4 :1


## Example 21.7 Page no 1092¶

In [33]:
#Given
b=2
u=1.33

#Calculation
b1=b/u

#Result
print"Fringe width is", round(b1,1),"mm"

Fringe width is 1.5 mm


## Example 21.8 Page no 1092¶

In [37]:
#Given
b2=0.4
b1=0.6
l1=5000

#Calculation
l2=(b2*2*l1)/b1

#Result
print"Wavelength of the light is", round(l2,0),"A"

Wavelength of the light is 6667.0 A


## Example 21.9 Page no 1092¶

In [42]:
#Given
d=0.125*10**-3                     #m
l=4500*10**-10                      #m
D=1                                 #m

#Calculation
x2=(2*D*l)/d
d1=2*x2

#Result
print"Separation between the fringes is", d1*10**3,"mm"

Separation between the fringes is 14.4 mm


## Example 21.10 Page no 1092¶

In [46]:
#Given
Imax=121
Imin=81.0

#Calculation
a=Imax/Imin

#Result
print"The ratio of intensity at the maxima and minima is",round(a,2)

The ratio of intensity at the maxima and minima is 1.49


## Example 21.13 Page no 1093¶

In [49]:
#Given
l=5.0                         #m
d=1                              #mm

#Calculation
a=d/l

#Result
print"Width of each slit is", a,"mm"

Width of each slit is 0.2 mm