3B Scientific Laser Optics Supplemental Set - Manual (Page 11)

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E17a Light beam passing through glass convex lens
– beam is parallel to the optical axis
(U17300/U17301)
A convex glass lens behaves as a convergent optical
system and the rays meet at figure focus F' after pass-
ing through the lens.
E17b Light beam passing through glass convex lens
– the rays are non-parallel to the optical axis
(U17300/U17301)
The plane
ϕ
' which is perpendicular to the optical axis,
combined with the figure focus F' is called a figure fo-
cus plane. If a beam of perpendicular rays impinges
the convex glass lens, the rays cross the plane
ϕ
' at
one point.
E17c Light beam passing through thick glass
convex lens
(U17301)
By inserting planparallel plates into the space between
two elements (23), a model of a thick lens can be con-
structed. The thickness d of the lens can be changed.
If the thickness increases the focal length of the lens
decreases. For a critical thickness the lens changes from
convergent to divergent.
E18a Light beam passing through glass concave
lens – the rays are parallel to the optical axis
(U17300/U17301)
The rays are divergent after passing a concave glass
lens, they do not create a real figure. By elongating the
rays it is seen that the lines have a common intersec-
tion – figure focus F'.
Air
Acrylic
Acrylic
Acrylic
Acrylic