Virtual Images & Initial Magnifying Power. By E. M. Nelson. 185 
follows: — A normal sighted person, whose least accommolating dis- 
tance is 8 in., uses a magnifying lens of 4 in. focus, the eye being 
placed at the posterior focal point. 
The magnifying power will be 2, that is, 1 less than that given 
in the table (formula ii.). Now, in order that a myopic eye, whose 
nearest distance of accommodation is 4 in., and which is held at 
the posterior focal point of the same lens, may see the image under 
the same visual angle, the object must be brought into contact with 
the lens. 
When an object is placed in contact with a thin lens, such as the 
spectacle lens under discussion, the magnifying power is unity ; in 
formula (ii.) when d = f, m = 1 ; this means that the image is the 
same size as the object, or, in other words, the magnifying power of 
the lens is entirely neutralized. This simple experiment, which can 
be tried by every one, proves that the amplifying power of every 
system is not the same for both, because the image is seen under the 
same visual angle. 
The truth is that, with the normal and myopic sight as defined 
in these examples, the amplification with the normal is twice as great 
as with the myopic sight. 
