# UNIT-3:Principle of Optics¶

## Example no:3.1,Page no:69¶

In [1]:
#Variable declaration
f=15.0           #focal length in cm
v=10.0          #image distance in cm

#Calculation
u=1/((1/v)-(1/f))  #calculating u using (1/f)=(1/v)-(1/u)

#Result
print"Object Distance ,u= ",u,"cm"

Object Distance ,u=  30.0 cm


## Example no:3.2,Page no:70¶

In [2]:
#Variable declaration
f=80.0      #focal length in cm
f1=20.0     #focallength of first lens in cm

#Calculation
f2=1/((1/f)-(1/f1))  #using (1/F)=(1/f1)+(1/f2)
P=(100.0/f)    #power in D
P1=100.0/20     #power of first lens
P2=P1-P     #power in D

#Variable declaration
print"Power= ",P2,"D"

Power=  3.75 D


## Example no:3.3,Page no:71¶

In [3]:
#Variable declaration
P=2.5      #Power in D

#Calculation
f=-(1/P)   #calculating f in m

#Result
print"Focal length =",f,"m"

Focal length = -0.4 m


## Example no:3.4,Page no:72¶

In [4]:
#Variable declaration
m=4      #magnigication
f=20     #focal length in cm

#Calculation
u=(20*3)/(4)   #on simplifying (1/f)=(1/v)-(1/u)
v=(4*u)   #calculating v in cm

#Result
print"Object distance,u= ",u,"cm"
print"Image distance,v= ",v,"cm"

Object distance,u=  15 cm
Image distance,v=  60 cm


## Example no:3.5,Page no:72¶

In [5]:
from scipy.optimize import fsolve

#Variable declaration
u=14.0     #object distance in cm
f=-21.0     #focal distance in cm

#Calculation
v=1/((1/f)-(1/u))
I=(3.0*v)/(-u)    #using m=(1/0)=(v/u)

#Result
print"Image distance= ",v,"cm"
print"I= ",I,"cm"

Image distance=  -8.4 cm
I=  1.8 cm


## Example no:3.6,Page no:79¶

In [6]:
#Variable declaration
fe=5   #focal length in cm
D=25   #distance od distinct vision in cm

#Calculation
m=1+(D/fe)   #calculating magnifying power

#Result
print"magnifying Power = ",m

magnifying Power =  6


## Example no:3.7,Page no:80¶

In [6]:
#Variable declaration
fe=5   #focal length in cm
D=25   #distance od distinct vision in cm

#Calculation
mo=30/(1+(D/fe))   #calculating magnification of objective lens

#Result
print"Magnification produced by objective lens = ",mo

Magnification produced by objective lens =  5


## Example no:3.8,Page no:80¶

In [7]:
#Variable declaration
u=-6.0     #object distance in cm
fo=4.0     #focal distance in cm
fe=6.0   #focal length in cm
D=25.0  #distance of distinct vision in cm

#Calculation
v=1/((1/u)+(1/fo))  #using (1/f)=(1/v)-(1/u)
m=(v/u)*(1+(D/fe))   #calculating m

#Result
print"Image distance in cm = ",v,"cm"
print"Magnifying Power = ",round(-m,2)

Image distance in cm =  12.0 cm
Magnifying Power =  10.33


## Example no:3.9,Page no:81¶

In [8]:
#Variable declaration
D=25.0         #distance of distinct vision
u=-9.0     #object distance in cm
fe=10.0   #focal length in cm

#Calculation
v=1/((1/fe)+(1/u))    #using (1/f)=(1/v)-(1/u)
m=(v/u)   #calculating m
M=D/u     #calculating Magnifying power of lens

#Result
print"Magnification of lens = ",m
print"Magnifying Power = ",round(-M,1)

Magnification of lens =  10.0
Magnifying Power =  2.8


## Example no:3.10,Page no:82¶

In [33]:
#Variable declaration
fo=0.5     #focal length of eye lens
D=25         #distance of distinct vision
L=15       #length in cm
m=375    #magnification

#Calculation
fe=(-L*D)/(fo*((L/fo)-m))   #calculating fe

#Result
print"Focal length of eye lens= ",round(fe,1),"cm"

Focal length of eye lens=  2.2 cm


## Example no:3.11,Page no:86¶

In [9]:
#Variable declaration
m=5     #magnifying power
L=24       #length in cm
fe=4    #focal length in cm

#Calculation
fo=5*fe   #calculating fo

#Result
print"Focal length of lens = ",fo,"cm"

Focal length of lens =  20 cm


## Example no:3.12,Page no:87¶

In [10]:
#Variable declaration
D=25.0         #distance of distinct vision in cm
fo=140.0     #focal length of eye lens
fe=5.0         #focal length in cm

#Calculation
m=-(fo/fe)    #calculating magnifying power
m1=-(fo/fe)*(1+(fe/D))     #calculating magnifying power

#Result
print"(a):Magnifying power at normal adjustment = ",m
print"(b):Magnifying power atleast distance of distinct vision = ",m1

(a):Magnifying power at normal adjustment =  -28.0
(b):Magnifying power atleast distance of distinct vision =  -33.6


## Example no:3.13,Page no:88¶

In [11]:
#Variable declaration
M=5          #Magnifying power
fo=10     #focal length of eye lens

#Calculation
fe=fo/M      #calculating fe

#Result
print"Focal length of eye lens= ",fe,"cm"

Focal length of eye lens=  2 cm


## Example no:3.14,Page no:88¶

In [12]:
#Variable declaration
fo=75.0     #focal length of eye lens
D=25.0         #distance of distinct vision
fe=5.0       #focal  of eye lens in cm

#Calculation
M=-(fo/fe)*(1+(fe/D))   #calculating M

#Result
print"Magnifying power = ",M

Magnifying power =  -18.0


## Example no:3.15,Page no:88¶

In [13]:
#Variable declaration
M=7       #magnifying power
L=40     #length

#Calculation
fe=(L/(M+1))   #focal length of eye lens in cm
fo=(M*fe)    #calculating focal length

#Result
print"Focal Length of lens=",fo,"cm"

Focal Length of lens= 35 cm