Everything about Photosensitivity totally explained
Photosensitivity is the amount to which an object reacts upon receiving
photons, especially
visible light.
Interpretation in medicine
Sensitivity of the
skin to a light source can take various forms. People with particular skin types are more sensitive to
sunburn. Particular medications make the skin more sensitive to sunlight; these include most of the
tetracycline antibiotics and the heart drug
amiodarone. Particular conditions lead to increased light sensitivity. Patients with
systemic lupus erythematosus experience skin symptoms after sunlight exposure; some types of
porphyria are aggravated by sunlight. All types of
skin cancer are linked to excessive sunlight exposure, and the rare hereditary condition
xeroderma pigmentosum (a defect in DNA repair) accelerates this risk manifold.
While the term "photoallergy" or "sunlight allergy" is commonly employed in many of the conditions mentioned, there's in fact no actual
allergy in the technical sense of the word.
Interpretation in electronic engineering
Certain electronic devices, such as
photodiodes and
charge-coupled devices, are designed to be sensitive to light. They are constructed to take advantage of the
photoelectric effect, the emission of electrons from matter upon the absorption of
electromagnetic radiation. When light (one form of electromagnetic radiation) impinges on the active surface of such a device,
electrical current flowing through or
electrical charge stored in the device will increase or decrease in proportion to the intensity and
wavelength of the light. This trait allows the device to perform regulating and sensing functions of many kinds. For example, a
photoresistor circuit may sense ambient light to turn on a street lamp at dusk.
Digital cameras use charge-coupled devices whose extreme sensitivity to light allows them to convert incoming photons into varying electrical charges with great accuracy. The varying charges are then encoded in a
binary file which can be stored and later viewed on a computer screen or other medium.
Interpretation in chemistry
Chemicals that are photosensitive may undergo
chemical reactions when exposed to light. These chemicals, such as
hydrogen peroxide and many prescription drugs, are stored in tinted or opaque containers until they're needed to prevent photodegradation. Devices that are photosensitive include the human
retina and
photographic film; their photosensitive materials undergo a chemical reaction when struck by light.
Typical substances that are photosensitive are
alkali salts and
silver halides.
Further Information
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