# Chapter 25 Interference of light¶

## Example 25.1 Page no 728¶

In :
#Given
w1=4
w2=9.0
a=25

#Calculation
I=w1/w2
Imax=a/1.0

#Result
print"Ratio of intensity is",Imax

Ratio of intensity is 25.0


## Example 25.2 Page no 728¶

In :
#Given
l=4800*10**-10                         #m
b=0.6*10**-2
b1=0.0045

#Calculation
a=l/b
l1=a*b1*2

#Result
print"Wavelenght of the light is", l1*10**10,"A"

Wavelenght of the light is 7200.0 A


## Example 25.3 Page no 728¶

In :
#Given
d=1.5*10**-3
D=1                                   #m
w=3.93                               #mm
D1=1.5

#Calculation
b=w/10.0
l=(b*10**-3*d)/D
a=(10*D1*l)/d

#Result
print"Wavelength of the light is", l,"m"
print"Width of 10 fringes is",a*10**3,"*10**-3 m"

Wavelength of the light is 5.895e-07 m
Width of 10 fringes is 5.895 *10**-3 m


## Example 25.4 Page no 729¶

In :
#Given
d=0.02                      #cm
D=80
l=6*10**-5
n=5

#Calculation
y5=n*D*l/d

#Result
print"Distance of fifth bright fringe is",y5,"cm"

Distance of fifth bright fringe is 1.2 cm


## Example 25.5 Page no 729¶

In :
#Given
d=3*10**-4
D=1.5
y4=10**-2                      #m

#Calculation
l=y4*d/(4*D)

#Result
print"Wavelength of light is",l,"m"

Wavelength of light is 5e-07 m


## Example 25.6 Page no 729¶

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

#Calculation
y2=2*D*l/d
y21=2*y2

#Result
print"Seperation between bright fringe on both sides of central maximum is",y21*10**3,"*10**-3 m"

Seperation between bright fringe on both sides of central maximum is 14.4 *10**-3 m


## Example 25.7 Page no 729¶

In :
#Given
d=0.012                      #m
D=100
l=6000*10**-8                   #cm
n=2

#Calculation
y2=(n**2+1)*D*l/(n*d)

#result
print"Distance of 3rd dark band is",y2,"cm"

Distance of 3rd dark band is 1.25 cm


## Example 25.8 Page no 729¶

In :
#Given
d=2*10**-4                  #m
D=1.5
y3=1.8*10**-2

#Calculation
l=2*y3*d/(7*D)

#Result
print"Wavelength of the light is", round(l*10**7,2)*10**-7,"m"

Wavelength of the light is 6.86e-07 m


## Example 25.9 Page no 729¶

In :
#Given
b=2*10**-3
l=6.0*10**-7
u=1.33

#calculation
l1=b/l
b2=(b*l)/(u*l)

#Result
print"Fringe width is",round(b2*10**3,2),"mm"

Fringe width is 1.5 mm


## Example 25.10 Page no 729¶

In :
#Given
l=6000*10**-10                    #m
d=10**-3
D=1
n=10

#Calculation
a10=n*l/d
b=(D*l)/d

#Result
print"(a) Angular position of 10th maximum is",a10,"radian"
print"(b) Separation of the two adjacent minima is",b*10**3,"mm"

(a) Angular position of 10th maximum is 0.006 radian
(b) Separation of the two adjacent minima is 0.6 mm


## Example 25.11 Page no 730¶

In :
#Given
l=6000*10**-10                                   #m
r=0
n=7

#Calculation
t=n*l/2.0

#Result
print"Difference of the film is", t,"m"

Difference of the film is 2.1e-06 m


## Example 25.12 Page no 730¶

In :
#Given
u=1.4
t=10**-4               #cm
n1=4.0
n2=5.0
n3=6.0
n4=7.0
N1=9
N2=11
N3=13

#Calculation
a=2*u*t*10**8
l1=a/n1
l2=a/n2
l3=a/n3
l4=a/n4
L1=2*a/N1
L2=2*a/N2
L3=2*a/N3

#Result
print"(i) Wavelength When the reflection is weak is",l1,"A ,",l2,"A ,",round(l3,0),"A ,",l4,"A"
print"(ii) Wavelength when the reflection is strong is",round(L1,0),"A ,",round(L2,0),"A ,",round(L3,0),"A"

(i) Wavelength When the reflection is weak is 7000.0 A , 5600.0 A , 4667.0 A , 4000.0 A
(ii) Wavelength when the reflection is strong is 6222.0 A , 5091.0 A , 4308.0 A


## Example 25.13 Page no 730¶

In :
#Given
n1=10
l1=4358*10**-10                   #m
l2=5893.0*10**-10

#Calculation
n2=n1*l1/l2

#Result
print"Number of fringes is",round(n2,1)

Number of fringes is 7.4