Physics, asked by gourav1549, 8 months ago

What is equivalent lens ? obtain an expression for the equivalent focal length of two thin lenses separated
by a distance d.​

Answers

Answered by harshitsood84
0

Answer:

Explanation:

Let the  focal lengths of the two lenses be f  

1

​  

 and f  

2

​  

.

u  

1

​  

=OC  

1

​  

 and

v  

1

​  

=I  

1

​  

C  

1

​  

 

u  

2

​  

=−C  

1

​  

I  

1

​  

 which is approximately equal to C  

2

​  

I  

1

​  

    and

v  

2

​  

=C  

2

​  

I which is approximately equal to C  

1

​  

I

∴  

u  

1

​  

 

1

​  

+  

v  

1

​  

 

1

​  

=  

f  

1

​  

 

1

​  

 

and  

u  

2

​  

 

1

​  

+  

v  

2

​  

 

1

​  

=  

f  

2

​  

 

1

​  

 

OC  

1

​  

 

1

​  

+  

I  

1

​  

C  

1

​  

 

1

​  

=  

f1

1

​  

 and

−C  

1

​  

I  

1

​  

 

1

​  

+  

C  

1

​  

I

1

​  

=  

f  

2

​  

 

1

​  

 

So  

OC  

1

​  

 

1

​  

+  

I  

1

​  

C  

1

​  

 

1

​  

=  

f  

1

​  

 

1

​  

+  

f  

2

​  

 

1

​  

=  

F

1

​  

.

Combined focal length of two thin lenses in contact is given by:

F=  

f  

1

​  

+f  

2

​  

 

f  

1

​  

f  

2

​  

 

​  

 

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