Electricity (from the New Latin ēlectricus, "amber-like"[a]) is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning and static electricity, but in addition, less familiar concepts, such as the electromagnetic field and electromagnetic induction.
Magnetism, a non-contact force, is a category of behavior of materials that respond at an atomic or subatomic level to an applied magnetic field. For example, the most well known form of magnetism is ferromagnetism such that some ferromagnetic materials produce their own persistent magnetic field. However, all materials are influenced to greater or lesser degree by the presence of a magnetic field. Some are attracted to a magnetic field (paramagnetism); others are repulsed by a magnetic field (diamagnetism); others have a much more complex relationship with an applied magnetic field. Substances that are negligibly affected by magnetic fields are known as non-magnetic substances. They include copper, aluminium, gases, and plastic.
The magnetic state (or phase) of a material depends on temperature (and other variables such as pressure and applied magnetic field) so that a material may exhibit more than one form of magnetism depending on its temperature, etc.
Light is electromagnetic radiation of a wavelength that is visible to the human eye (in a range from about 380 or 400 nanometres to about 760 or 780 nm).[1] In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not.
Five primary properties of light are intensity, frequency or wavelength, polarization, phase and orbital angular momentum.
Light, which exists in tiny "packets" called photons, exhibits properties of both waves and particles. This property is referred to as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.
Refraction is the bending of light rays when passing from one transparent material to another. It is described by Snell's Law:
n_1\sin\theta_1 = n_2\sin\theta_2\ .
where θ1 is the angle between the ray and the normal in the first medium, θ2 is the angle between the ray and the normal in the second medium, and n1 and n2 are the indices of refraction, n = 1 in a vacuum and n > 1 in a transparent substance.
Interference (wave propagation)
In physics, interference is the addition (superposition) of two or more waves that results in a new wave pattern. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency.
A mirror is an object with at least one reflective surface. The most familiar type of mirror is the plane mirror, which has a flat surface. Curved mirrors are also used, to produce magnified or diminished images or focus light or simply distort the reflected image.
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A lunar eclipse occurs when the moon passes through the shadow of the earth. A lunar eclipse can last up to an hour and a half. During a lunar eclipse the moon may turn a reddish color. It is not dangerous at all to look at a lunar eclipse because the moon does not make its own light.
Animation by Stephen Gray using photos © James Funkhouser.
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Photograph © James Funkhouser.
A Solar Eclipse occurs when the moon goes in front of the sun and blocks most of the sun's light from the earth. During a total eclipse all you can see from earth is a ring of light around the moon which is part of the sun the moon did not cover. It is dangerous to look at a solar eclipse directly, even if you have sun glasses or smoked glass. It is better to view solar eclipses through a pin hole projector.
A curved mirror is a mirror with a curved reflective surface, which may be either convex (bulging outward) or concave (bulging inward).A convex mirror, fish eye mirror or diverging mirror, is a curved mirror in which the reflective surface bulges toward the light source. Convex mirrors reflect light outwards, therefore they are not used to focus light.
A concave mirror, or converging mirror, has a reflecting surface that bulges inward (away from the incident light). Concave mirrors reflect light inward to one focal point, therefore they are used to focus light.
A real image of an object produces the same pattern of light as the object does somewhere in space. Some portion of the light from the real image reaches our detector along a straight-line path. The detector cannot distinguish between light coming from the object and light coming from the image. We interpret the same patterns in the same way.
A virtual image is the apparent position from which a pattern of light reaches our detector, if we make the assumption that it has traveled from its source to the detector along a straight-line path. Virtual images are formed when light from an object or from an image is reflected or bend on the way to the detector.
