- 1 reason for seeing the sunlight during the day only
- 2 About sunlight
- 3 day polar night and polar
- 4 References
The reason for seeing the sunlight during the day only
Is a succession of night and day one of the most important cosmic phenomena that we see in our daily lives, and the biggest blessings that make our lives go with equanimity and harmony with the nature of the human body, where the night happens and the day as a result of the rotation of the earth around the same time every 24 hours, it rotates from west to east on its axis phantom oblique, and at the same time, it also revolves around the sun, and because of this rotation and because the Earth's axis slant, the length of the day and night may vary from region to region, and from chapter to another, and some areas may pass them long days without to see the light as the sun at the poles. 
The light that illuminates the Earth is an energy that travels in the form of waves in the electromagnetic spectrum that nine-sun,  and consists of this spectrum from a group of radiation divided by wavelength, a shorter for longer: gamma rays, X-rays, UV , visible light, infrared, microwave radiation (very short), radio-rays. 
When this spectrum up the atmosphere of the Earth based air molecules analyzed some of the parts according to the wavelength of each part by the previously mentioned groups,  also called visible light by this name because it is the only group with visible wavelengths of the eye Aelmejrdh. 
Polar day and night polar
The earth revolves around the sun with a deviation of $ 23.5 degrees towards the sun, and as a result of this deviation, one of the poles will be exposed to the sun for a period of approximately 6 consecutive months, which means that this pole will not see the night in this period, the day is called in this region (daytime polar) In the same period, the other pole will not reach of 6 months is also the sun's rays, and called the night (polar night), and in the six months following the exchange poles of the sun for their position Viaaqub day and night on them. 
- ↑ MATT WILLIAMS (11-12-2014), "What Causes Day and Night?"، universetoday, Retrieved 1-10-2018. Edited.
- ^ أ ب Jim Lucas (30-4-2015), "What Is Visible Light?"، Live Science, Retrieved 1-10-2018. Edited.
- ↑ Jim Lucas (12-3-2015), "What Is Electromagnetic Radiation?"، Live Science, Retrieved 1-10-2018. Edited.
- ↑ Robert Roy Britt (9-6-2014), "Why Is the Sky Blue?"، Live Science, Retrieved 1-10-2018. Edited.
- ↑ "Polar day - polar night", meteoblue, Retrieved 9-10-2018. Edited.
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