There are several reasons
when there is no position forms a clear image because of defect in
lens and these defects are :-
- Spherical Aberation
:- When parallel beam of light strikes the lens they
converge to different points due to which multiple images are
formed at near by points which gets partly superimposed to form the
resultant image which is blurred . This defect is known as
Spherical Aberation .
- Chromatic
Aberation:- When white light strikes a lens it breaks in
to spectrum dur to which each colour has it's own focus .These
multiple focus produce multiple images at near by points to produce
a resultant image which is blurred . This defect is known as
Chromatic aberation .
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