2. Light reflected from any smooth non diffusing
Surface is said to be polarized or plane polarized .
Eg :- snow,water
Glare is commonly caused by reflection from
water ,snow ,high waves and metallic surfaces .
A special group of filter in addition to absorbing
unwanted radiation also absorbs plane polarized
light the polarized light usually having been
produced by reflection .
3. Polarized light is different in character from
ordinary light or unpolarized light may be
represented by wave motion which is
vibrating in every direction .
4. Polarized light vibration in one direction only .
When unpolarized light is reflected by certain
substances or reflected from a non metallic
surface ,it becomes plane polarized its
vibration being restricted to one meridian
only .
5. Only if the light rays which are forming a
Brewster angle will be total polarized light .
6.
7.
8. Polarizing filter eliminate horizontal reflected
radiation .
In case of reflected light the degree of
polarization depends on the incidence and
reaches a maximum .
When the angle b/w the reflected and the
refracted beam is 900
This critical angle of incidence is known as
Brewster’s angle .
9.
10. A polarizing filter will only transmit plane
polarized light if the plane of vibration of light
is parallel to the polarizing axis of the filter .
If the plane of vibration is at right angle to the
polarizing axis the polarized light is absorbed .
The reflected light is totally plane polarized
the plane of vibration being horizontal such
that parallel to the reflecting surface .
11. If the polarizing filter is placed in the path of
the reflected light with its polarizing angle at
right angle to the reflecting surface such that
vertical it absorbs the reflected light .
12. The original polarizing filters were produced
by sandwiching microscopic crystals of
sulphate of quinine b/w two thin sheets of
cellulose acetate .
The axis of crystal being made to coincide by
placing the sheet in an electrical field .
13. The modern filter are however made by
stretching a thin sheet of PVA polyvinyl
alcohol so that the molecular structure of the
sheet is straightened into a chain which are
lying parallel to the direction of stretch .
The sheet is then dipped into iodine which is
absorbed by the sheet transforming it
immediately into a polarizing filter .
14. The thin polarizing sheet is finally sandwiched
b/w two sheets of cellulose acetate and is
pressed b/w two ground glass .
Alternatively the thin polarizing filter may be
sandwiched between two glass lenses and any
desired power can be incorporated into the
filter .
15. Decreased driving fatigue specially during day
time .
Fisherman can see more with polarizing
lenses because it not only removes reflected
or discomfort glare but enables the wearer to
see below the surface .
Anglers derive great benefit from this filters
because they can be see in water clearly
without the distraction of surface distortion .
16.
17.
18. Comfort at the beach is increased because sand
and water are both source of polarized glare
marking these lenses especially appropriate .
Color is not bleached.
Bright snowy rays are not blinding when viewed
with polarizing lenses .
Polarizing lenses are good alternative to
sunglasses because they inhibit U.V radiation .
19. All lenses such as bifocal ,single vision
,progressives can be made polarized .
Any material of lenses and can be made
polarized .
20. In polarizing lenses ,the color will appear a
normal as against sunglasses.
Can be demonstrated by showing a glossy
magazine or books .
Polarizing charts are provided by companies
which contain a word which can’t be seen by
naked eye and can be seen with polarizing
lenses.
21. It is possible to take two Plano polarizing
lenses and by holding one before the other
with their polarizing axis crossed at 900
eliminate all incoming visible light rays .
