Solve this: 26 For achromatic combination of lenses, if we use two lenses to focal length f length - Physics - Ray Optics And Optical Instruments

Question

Solve this:

26 For achromatic combination of lenses, if we use two lenses to
focal length f length f and f
respectively and dispersive power ω and ω '
then
( 1 )   ω = ω ∘ ,      
    ω ' = 2 ω ∘ ,   f ' = 2 f
          ( 2 )   ω = ω
∘ ,           ω ' = 2 ω
∘ ,   f ' - 2 f ( 3 )   ω = ω ∘ ,
          ω ' = 2 ω ∘ ,
  f ' = f 2           ( 4 )  
ω = ω ∘ ,          
ω ' = 2 ω ∘ ,   f ' = - f 2

Pintu B. · Accepted Answer

Dear Student ,
As we know that in case of the achromatic combination of lenses
product of the sum of their power and the dispersive is equal to
zero
Therefore we can write that ,ωf+ω'f'=0Now the above will only satisfy if we take that ,ω=ω0 , ω'=2ω0 and f'=-2fThus here the option (2) is correct 
Regards