TC, SP A parallel beam is one which does not diverge or converge - its width stays the same as the wave (which could be light or microwaves for example) travels out from its source. Parallel beams are [..]

UE An electrical appliance which is double insulated does not have an earth wire fitted. The appliance is designed in such a way that the electrical parts can never come into contact with the outer c [..]

TC, SP This applies to light rays passing through any system of mirrors or lenses. Basically, it means if a ray of light follows a path when going, say, from left to right, then another ray of light [..]

This is a phrase often uttered by those people who finish reading the zenith entry below, having read the whole of this file. Top Z Zenith SP The zenith is the point in the sky directly above an obse [..]

TC Deflection plates are used to direct the electron beam to all parts of the cathode ray tube of an oscilloscope. There are two sets of plates, one set for controlling horizontal movement of the bea [..]

HP, EL, EM, SP An atom is the smallest possible particle of any chemical element. For example, an atom of carbon is the smallest possible unit of carbon. All of the atoms of an element are identical [..]

TC, HP X-rays were discovered accidentally by Wilhelm Röntgen in 1895. X-ray radiation is a part of the electromagnetic spectrum. With wavelengths ranging from about 0.001nm to about 100 nm, X-rays a [..]

EM def

TR, EM When a force acts on a moving object, that force does mechanical work. The work done is defined by the equation: Work Done = Force x Distance The SI unit of work is the same as that of energ [..]

TC, UE, HP, SP A travelling disturbance, carrying energy from place to place. Examples are water waves and sound waves where it is the movement of particles which constitutes the wave motion. In the e [..]