To understand it better, a comparison with a similar phenomenon in sound waves called Doppler Effect is used. Imagine that you are riding in the car moving towards the north when suddenly an ambulance passes by going in the opposite direction. You will notice that as you and the ambulance move closer to each other you will hear a higher frequency of the siren while as you move farther away from each other, you will hear a lower frequency of sound. Light behaves in a similar way because it has wave-like properties.

With regards to astronomy, the universe has been known to be continuously expanding and along with it galaxies tend to move away from us. Accordingly, the light emanating from these galaxies is redshifted or change into longer wavelengths. This shift isn’t observed by the naked eye and is usually measured by comparing the spectrum produced by this light to that of a reference laboratory spectrum. By comparing the spectrum to known wavelengths, astronomers are able to determine the redshift occurring from these distant sources.

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Depending on the application, the exact angles between each surface differs. Traditionally, a prism is that of a triangular prism, with a triangle shaped base and rectangular sides. Most prisms are made of glass, though it can also be made of other transparent material, equal to the wavelength to which they are meant to be used.

It can be used to break up light to its equivalent spectral colors, which include the colors red, orange, yellow, green, blue, indigo and violet. It can also reflect light or even split light into various wavelength.

Prisms work in dependence to light. As the speed light changes from one medium to another (e.g. light from air and into the section of the prism), it then causes light to be refracted and then enter the new medium, this time at a different angle or view. This is the basic principle of using a prism. Aside from this, the angle or the bending level of the light is hugely dependent on the angle where the light hit the object, and also varies in terms of wavelength due to the refractive ratio of the two light gathering objects.

There are also other types of prism: namely, the dispersing, grating, reflecting and polarizing types. The dispersing prism is the common type, where it breaks light into spectral colors. Grating prisms are used for light diffraction or splitting. Reflecting prisms are used in binoculars to reflect light. And polarizing on the other hand is used for splitting light into different spectrums.

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Photometry is often carried out using photometers. Photometers have been used since the early days of astronomy and most astronomers build specialized photometers for specific telescopes. The simplest method of doing photometry is by utilizing an astronomical telescope and specialized optical filters. Once the radiation is received through the telescope, it passes through the optical filters and a photosensitive instrument captures and records the intensity. Measuring the light in the near infrared to the ultraviolet spectrum typically requires the use of photoelectric photometers and today, CCD cameras are slowly replacing these photometers. CCD cameras can take multiple shots of a particular celestial object in study and later on processed to extract the intensity values based on the snapshots.

Photometry despite the simplicity of the concept is a very complicated study of celestial objects based in the light they emit. But the light provides astronomers with many hints on the orbital periods of binary stars, a small planet’s rotating period and the strength of a supernova based on the energy released.

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Thus, everything in the universe can be analyzed using infrared detectors, including those that are very distant from the earth. Stars and heavenly bodies emit infrared wavelengths between 1 and 300 microns. These are not detectible by the human eye, but infrared instruments can identify them and glean important characteristics from the type of the radiation. In effect, infrared detectors can see what would otherwise be invisible and unknowable if only the naked eye and telescopes are used.

Light or electromagnetic radiation is of various wavelengths. Only a small fraction of these radiations are actually visible to people. The more distant the source of the radiation, the harder it is for the human senses to detect them. Galaxies are incredibly far, far away, and it is estimated that the human eye can see only less than 1% of the radiation they emit. It is a good thing then that infrared detectors have been invented to help astronomers uncover the wealth of information coming from all around the universe through infrared radiation.

Some infrared detectors were sent out in space, so that they can better detect electromagnetic signals without interference from the earth’s atmosphere. They detect various kinds of radiation within the infrared region, including near-infrared light, which refers to infrared wavelengths that are closest to visible light. There too is far-infrared light, referring to wavelengths farthest from visible light and closer to microwave radiation. In between the two is mid-infrared light.

Aside from infrared radiation and visible light, there too are gamma rays, X-rays, ultraviolet, microwave light, and radio waves. With the help of various instruments, astronomers study all these types of radiation coming from different parts of the universe to uncover more information.

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The study of subatomic particles like neutrinos normally lie within the realm of physics, but it is in astronomy that scientists are able to study neutrinos in action. For example, in 1968, an experiment was able to detect neutrinos produced by the burning gases on the sun’s surface. And in 1987, a burst of neutrinos was detected from the explosion of a supernova.

This 1987 event marked the “official” beginning of a branch of science called neutrino astronomy: a kind of a marriage between physics and astronomy whose main objective is to shed light on the nature and characteristics of neutrinos.

So far, three types of neutrinos have been discovered: the electron-neutrino, the tau-neutrino and the muon-neutrino. They, together with electrons, are classified as leptons. Leptons and quarks— collectively known as Fermions—are the fundamental building blocks of the universe.

Understanding Neutrinos

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Physical optics is focused on the nature, creation and properties of light. It is generally referred to as approximation, used also in electrical engineering and applied physics. In optics, it estimates interference, diffraction, and polarization.

Psychological optics, on the other hand, tackles on the role of light in vision. Visual observations are primary considerations as the power of the brain and the eye is being tested.
Reflection and refraction of light are both dealt with in Geometrical optics. Mirrors, lenses and optical fibers are deliberated here.

There are many other modern and practical uses of Optics. More and more studies are being undertaken to learn other uses of light. With Scientific Revolution underway, modern developments tend to become overflowing with theories strengthening more its backbone.

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In physics, focus is defined as that point in which the rays of light converge or meet; or diverge in the case when light is refracted or reflected. In optics, it can mean a number of things including:

? A lens? focal point
? A lens? or a telescope?s eyepiece?s focal length
? The condition by which an object being viewed through an optical system is seen; either being in or out of focus
? A device used in optical systems in order to adjust its focal length, thereby making an image clearer

An image is in focus when the light from the object converges on almost one single point in the image, while an object out of focus will have light from it not converging very well.

In astronomy, interest in foci is usually concentrated to telescope use. To get a good view of distant objects in the sky, a telescope must be properly focused. Focusing of telescopes is easy, and comes instinctively even to beginners.

Adjusting the focus of a telescope is usually done either by moving its eyepiece or its primary mirror. This can be done by turning the wheels of a geared system, called the rack and pinion; or by turning a screw knob on the back of a telescope.

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Photo by: Dim Grits Creative Commons

A variable star is a star which has varying brightness as viewed from earth. The brightness can change in a matter of seconds or even years, and the intensity of brightness can vary from as low as thousandth of a magnitude, which can only be seen by a powerful telescope, to as great as 20 magnitudes that can be seen by the naked eye.

Variable stars are classified as either intrinsic or extrinsic, depending on the cause of the variations in brightness. Intrinsic variable stars are those whose fluctuations in brightness are caused by the physical changes occurring in the star itself. It is further divided into subtypes: Pulsating, Eruptive, and Cataclysmic.

The variation may be caused by the pulsation or eruption in the star. Pulsating variable stars actually shrink or swell because of the forces inside the star. In Eruptive variable star, there are flares or ejections from the star, which cause the fluctuations. Another subtype of intrinsic variable star is the cataclysmic variable wherein there is an outburst of stellar material into space causing intense brightness. Supernovas are popular examples.

The second type of variable star, the extrinsic type is primarily caused by the eclipse of one star to another in a binary system. It may also be caused by the stellar rotation. The variability in rotating variable occurs when the star rotates and the side that is seen from the earth is the darker side of the star.

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Interferometry

This type of study is vital and essential in astronomy, since the way to study celestial bodies or even the universe is through the means of electromagnetic, sound or light waves. This means that it passes through a medium, much like a science experiment that once a tuning fork is rocked, it emits vibrations.

In science, the most atoms emit light only at radio wavelengths, while gases from celestial bodies like planets, quasars, pulsar are easily detected using these radio waves, and this kind of waves pave the way to know more about the universe and the galaxies.

Also, interferometry uses the concept of superimposition of wavelengths in physics. This means that most astronomers try to combine separate variations of wavelengths in a certain manner that the results of the waves have come up with a meaningful output based on the original forms of the combined wavelengths, especially when the frequency of the waves are the same.

Basic Interferometry, Explained

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Light pollution

Pollution happens during the production of artificial light. There are several scientific meanings of Light pollution. These include:

• Light pollution is the adjustment of light due to artificial light resources.
• Light pollution is the excessive production of artificial light which adversely affect the light levels.

All these refers to the introduction of man-made structures that produce artificial light.

What light pollution does is that it reduces the visibility in the evening sky. It does not allow people to appreciate the beauty of the heavens. It also disrupts astronomers in their study of space. Such pollution is known to distract existing ecosystems not to mention negative health effects.

This type of pollution is one of the consequences of the industrial revolution. As cities become more and more urbanized, one may observe a heightened degree of Light pollution. This is a very dangerous predicament in our ever-developing world.

What is Light Pollution?

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