Glass and plastic become optically active when stressed; the greater the stress, the greater the effect. Optical stress analysis on complicated shapes can be performed by making plastic models of them and observing them through crossed filters, as seen in
[link] . It is apparent that the effect depends on wavelength as well as stress. The wavelength dependence is sometimes also used for artistic purposes.
Another interesting phenomenon associated with polarized light is the ability of some crystals to split an unpolarized beam of light into two. Such crystals are said to be
birefringent (see
[link] ). Each of the separated rays has a specific polarization. One behaves normally and is called the ordinary ray, whereas the other does not obey Snell’s law and is called the extraordinary ray. Birefringent crystals can be used to produce polarized beams from unpolarized light. Some birefringent materials preferentially absorb one of the polarizations. These materials are called dichroic and can produce polarization by this preferential absorption. This is fundamentally how polarizing filters and other polarizers work. The interested reader is invited to further pursue the numerous properties of materials related to polarization.
Section summary
Polarization is the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave.
EM waves are transverse waves that may be polarized.
The direction of polarization is defined to be the direction parallel to the electric field of the EM wave.
Unpolarized light is composed of many rays having random polarization directions.
Light can be polarized by passing it through a polarizing filter or other polarizing material. The intensity
of polarized light after passing through a polarizing filter is
where
is the original intensity and
is the angle between the direction of polarization and the axis of the filter.
Polarization is also produced by reflection.
Brewster’s law states that reflected light will be completely polarized at the angle of reflection
, known as Brewster’s angle, given by a statement known as Brewster’s law:
, where
is the medium in which the incident and reflected light travel and
is the index of refraction of the medium that forms the interface that reflects the light.
Polarization can also be produced by scattering.
There are a number of types of optically active substances that rotate the direction of polarization of light passing through them.
Conceptual questions
Under what circumstances is the phase of light changed by reflection? Is the phase related to polarization?
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life