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Physics is considered to be the most basic of the natural sciences. It deals with the fundamental constituents of matter and their interactions as well as the nature of atoms and the build-up of molecules and condensed matter. It tries to give unified description of the behavior of matter as well as of radiation, covering as many types of phenomena as possible. In some of its applications it comes close to the classical areas of chemistry, and in others there are clear connections to the phenomena traditionally studied by astronomers. Present trends are even pointing toward a closer approach of some areas of physics and microbiology.


Different forms of energy spread across a range called the electromagnetic spectrum. Energy forms in this spectrum have both electrical and magneticcharacteristics. They travel as electromagnetic waves. All waves have wavelength and frequency. A wave has an uppermost crest and a bottommost trough.

Wavelength is the distance between the crest of one wave and the next (or between the trough of one wave and the next). Wavelength may be expressed in millimicrones. Frequency is the number of waves that pass a given point in a given time. Frequency is expressed in hertz, or cycles per second. An inverse relationship exists in the electromagnetic spectrum. As the wavelengths of energy forms grow longer, their frequencies diminish. Gamma rays have the shortest wavelengths and the highest frequencies; long radio waves have the longest wavelengths and the lowest frequencies. We can directly sense only a small portion of the electromagnetic spectrum. We can see visible light and feel the heat of infrared rays. Other forms require instruments that convert the energy into perceptible forms, such as gamma ray counters or radio receivers.



What are industrial robots and how do they work? Although they vary widely in shape, size and capability, industrial robots are made up of several basic components: the manipulator, the control and the power supply.

The manipulator is the mechanical device, which actually performs the useful functions of the robot. It is a hydraulically, pneumatically or electrically driven jointed mechanism capable of number independent coordinated motions. Feedback devices on the manipulators joints or actuators provide information regarding its motions and positions to the robot control. A gripping device or tool, designed for the specific tasks to be done by the robot, is mounted on the outermost joint of the manipulator. Its function is directed by the robots control system.

The control stores the desired motions of the robot and their sequence in its memory; directs the manipulator through this sequence or program upon command; and interacts with the machines, conveyors and tools with which the robot works. Controls range in complexity from simple stepping switches to minicomputers.



X-rays are forms of radiation higher on the electro-magnetic spectrum than closely related ultraviolet waves. X-rays have great penetrating power because their short wavelength and high frequency let them travel easily between the atoms of a substance. X-rays are emitted from many sources in the universe. They can also be generated for medical and industrial uses. When photographic film is placed behind an object being X-rayed, the developed roentgenogram reveals a shadow picture of the object. For instance, when a hand is X-rayed, the roentgenogram shows the bones of the hand as white shapes against a black background. This is because X-rays do not penetrate the dense flesh and thus do not expose (darken) the areas of the film covered by the bones. X-rays can be produced by high-vacuum X-ray tubes.

Such tubes consist of an airtight glass container with two electrodes one positive and one negative sealed inside. The cathode, or negative electrode, has a small coil of wire. The anode, or positive electrode, consists of a block of metal. An electric current flows through the cathode, causing it to become extremely hot. The heat releases electrons from the cathode. At the same time, a high voltage is applied across the cathode and the anode. This voltage forces the electrons to travel at high speeds towards the tungsten target. When the electrons strike the target, X-rays are produced.


Date: 2016-01-14; view: 59

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