Lighting Two
Lighting Two
If light from two stars overlaps on a screen, is an interference pattern produced? What conditions must be sa?
If light from two stars overlaps on a screen, is an interference pattern produced? What conditions must be satisfied to produce such a pattern?
Its an interesting idea. If the two beams of light from these two stars just overlap on a screen, the brightness of the image will either be brighter or dimmer than either beam alone. That depends on the "phase" of the two beams of light as they overlap. If their phase is "in phase or constructive" the sum beam of light will be brighter than the individual beam alone; likewise, if the two beams are out of phase, destructive, than the combined beam will be dimmer than the two individual beams alone.
As such, there wouldn't be an interference pattern between the two beams. However, if you brought the two beam together in a constructive phase, and projected them in to double splits, and then on to a screen behind the splits, you would get interference patterns.
Nevertheless, it is not clear to me just what those interference pattern would tell you about the nature of the light from the two stars. Nonetheless, further analysis might discover something significant. Who knows?
You might ask this question on Astronomy and Space
"Interference: The phenomenon in which 2 or more waves can reinforce each other (constructive interference) or cancel each other out (destructive interference)."
"Interferometer: An optical apparatus in which 2 or more light beams are split, redirected, and combined by beam splitters, demonstrating interference effects."
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Light Therapy During the Winter Seasons
When the sky is grey and the days grow short our morale is unharmed. Everyone can be affected by the loss of light in the dead season. It is now or never to chase away the passing blues or the seasonal depression with the help of light therapy.
A quarter of the population sees their life turned upside down by the season’s rhythm, where as 2 or 3% of people suffer a severe depression due to this time of year. It is only since the middle of the 80’s that researchers started looking for the reasons of this depressive state. Someone suffering from seasonal depressions have a tendancy to see their appetite increase, have a taste for sugar and have an excessive need for sleep. As the symptoms are different to a regular depression, Dr Marc Hébert researcher and professor at Laval Robert Giffard University, thinks it is necessary to treat patients differently. Instead of giving them a percription for antidepressants he praises a healthier solution : exposure to light.
The eye : window to the brain
“Contrary to what many people think the eye is not an external organ, but an extention of the brain” explains Dr Hébert. All the plays between the two ears, but as it is extremely difficult to study the organ in vivo, the study of the eye is composed of an interesting window.
If the brain seems to be affected by the lack of light, we do not know what makes certain people more vulnerable than others. It is by analysis of the retina that multidisciplinary directed by Dr Hébert, composed of researchers in neuroscience in opthalmologyof psychologists and psychiatrists resulting in knowing a little more about the role of light on the brain. “Alot of sick neuropsychiatrists think that the eye is the vision of the person not affected, he says (...) we are capable of studyin neurotransmitters presents the eye and we can see the effects after four weeks of light therapy sessions.”
Seratonine and dopamine are the two most common neurotransmitters that are directly linked to the humour. If there is a chemical inbalance of the neurotransmitters it can start a depression.
Light therapy
Light therapy, lux therapy or photo therapy consists of exposure to an intense light at eye level of 5000 to 10 000 lux (light unities), in controled conditions. A headline comparison, of regular lighting that we can have at the house or at the office of only 100 to 150 lux.
The advantage of this treatement is that it can be done at home. A light therapy lamp costs about 250 $. Certain pharmacies also offer a months trial. The cost of renting deducted if the person decides to buy the lamp. It is better to buy a lamp specially made for this effect rather than fabricate your own, says the specialist (it is a danger for the eyes and your skin).
The use of a light therapy lamp can be diversified, because the user can stay active during sessions. Dr Hébert personnaly uses all the time a lamp at work at his desk. He suggests also to people to put it on the table while they are having breakfast or when they are reading a news paper. The person should keep their eyes open, but not to keep looking at the light. The person can then carry on about their business, while being exposed to the light. You can equalise the sessions of exposur and the intensity of the light by your own energy and needs, which can change each month each year. After an hour a day, the benefits generally show about a week later. Sure it is firstly recommended to consult a doctor so as to decide if the problem which is affecting the person is actually seasonal depression.
Sceptics
Despite its benefits, light therapy still has scepitcs in the medical community. “There are psychologists and psychiatrists who do not believe in it, underlines Dr Marc Hébert. They were surprised to find that a number of patients replied in the same way to light therapy sessions”. In fact, it would seem that the treatment works for about 70% of people suffering from seasonal depression. One of the advantages of this treatment is the possibility which it offers to everyone, the power to anticipate the blues before the arrival of autumn.
“We know that the treatment of light therapy works for people affected by winter depression, but we do not know yet the mecanical theraputic action, indicates Dr Marc Hébert, who specialises in the subject since 1992. We notice that the biological response to the light therapy, which lets us conclude that it, is not a placebo effect, but a real effect”.
According to Kino Québec, a person has “more chance of being in a good mood and have the spirit if his level of melotonin (sleeping hormone) is not too high during the day” the exposure to the light helps to increase the level of mealtonin. The govermental organisations suggest the practise of sports outside even when it is dull, seeing as the light of day will always be superior to the light we find in doors. Although, the Russian acadamy of medical science showed that physical exercise also had positive results, as light therapy for people suffering from Seasonal Affective Disorder.
If the idea of being exposed to artificail light puts you off, nothing stops you from changing your habits and going to enjoy the sun summer or winter. It must be known that the sun produces 100 000 lux during the summer, but the intensity of the light is lower in winter, so only 20 000 lux on average. The statistiques show that during summer the daily exposure during the day is about 2 hours so during winter it is just 30 minutes. Never forget that the intensity of the sun is about 25 times more powerful than a light therapy lamp.
You will find all the information you need on light therapy on the specialist site : Solvital
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solvital light therapy provides all information on bright light therapy, dawn simulator/ and also light therapy glasses Luminette
Lighting Two
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