Fundamentals of geometrical optics
Refracting power, relationship between f and f'
The optical system is defined by (H, H', F, F').
Figure 37
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Let us consider an object point B situated on the object focal plane. Its image B' is to infinity. Foloowing figure 37, the ray BI parallel to the axis (red) has for an image I'F' forming the angle θ' with the axis as all emerging rays since image B' is to infinity.
Ray BH (blue) has for image a ray issued from H' (image of H) and forming an angle θ'. The relationship (20) applied to the conjugation (HH') gives us : nθ= n'θ' or θ= y/f and θ'=-y/f ' From this we deduct Cv being the system refracting power :