What color do you see in the light reaching us from the sun? Separating sunlight into its component wavelengths results in the spectrum shown below. The greatest amount of sunlight is emitted at wavelengths around nanometers, so you can easily see why sunlight appears yellow.
This spectrum matches the spectrum of light emitted by an object at 6, degrees Kelvin in temperature, which backs up the previously mentioned fact that the surface temperature of the sun is 6, degrees Kelvin. As you can see, the spectrum of electromagnetic waves emitted by a heated object can be used to figure out its temperature. For example, Sirius, a bluish-white first magnitude star in the constellation Canis Major, is known to have a high surface temperature exceeding 10, degrees Kelvin.
You have undoubtedly noticed that the sun appears yellow rather than bright red. The kind of light detectable by the human eye is called visible light, which has a wavelength between around to nanometers. The human eye is said to be most sensitive to light in wavelengths around nanometers. It is believed that the reason behind this sensitivity is the evolution of the human eye by adaptation to the solar spectrum. If the sun were a much hotter star, the range of visible light would have been different.
However, the environment on present-day earth would likely be far different, and it is doubtful that human beings and other organisms would ever come into being. Chapter 1: The Mysteries of Light.
Energy is released because the helium nucleus has a slightly lower mass than the four original hydrogen nuclei. This energy eventually makes its way to the outer regions of the sun and is radiated or emitted away in the form of energy, known as electromagnetic radiation. A particle of electromagnetic radiation is known as a photon.
Electromagnetic radiation, also known as radiant energy or radiation , is spread in the form of electromagnetic waves. Electromagnetic waves are waves that can cause charged particles such as electrons to move up and down.
These waves have both electrical and magnetic properties and can travel through gases, liquids, solids, and through empty space or a vacuum at nearly , kilometers per second the speed of light. This axis of rotation is tilted The axis of rotation is pointed toward Polaris, the North Star. When it is summer solstice in the Northern Hemisphere, it is winter solstice in the Southern Hemisphere.
Winter solstice for the Northern Hemisphere happens on December 21 or With fewer daylight hours in winter, there is also less time for the Sun to warm the area.
When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere. The daylight and nighttime hours are exactly equal on an equinox. The autumnal equinox happens on September 22 or 23 and the vernal or spring equinox happens March 21 or 22 in the Northern Hemisphere. The progression of electromagnetic radiation through space can be visualized in different ways. Some experiments suggest that these rays travel in the form of waves. A physicist can actually measure the length of those waves simply called their wavelength.
It turns out that a smaller wavelength means more energy. At other times, it is more plausible to describe electromagnetic radiation as being contained and traveling in little packets, called photons. The distinguishing factor among the different types of electromagnetic radiation is their energy content. Ultraviolet radiation is more energetic than visible radiation and therefore has a shorter wavelength. To be more specific: Ultraviolet rays have a wavelength between approximately nanometers and nanometers whereas visible radiation includes wavelengths between and nanometers.
The sun is a major source of ultraviolet rays. Man-made lamps can also emit UV radiation, and are often used for experimental purposes. Light enables us to see, and heat keeps us from being cold. However, ultraviolet rays often carry the unfortunate circumstance of containing too much energy. For example, infrared rays create heat in much the same way as rubbing your hands together does. The energy contained in the infrared rays causes the molecules of the substance it hits to vibrate back and forth.
However, the energy contained in ultraviolet rays is higher, so instead of just causing the molecules to shake, it actually can knock electrons away from the atoms, or causes molecules to split.
This results in a change in the chemical structure of the molecule.
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