Man's physical universe

xanabras

528 MAGNETISM AND ELECTRICITY

well's theory, waves would be set up which would travel out in all

directions from the vibrating electron. A luminous body is considered

to have within it countless vibrating electrons passing from one

energy level to another, which cause the electromagnetic waves that

we call light. A heated, nonluminous body would also contain vibrating

electrons, but the amplitude of the vibration would differ from that

in a luminous body, and the wave length of the resulting electromagnetic

waves would therefore be different. In this case such waves

would be called infrared, or heat, waves.

Hertz Produced Electromagnetic Waves by an Oscillating Electric

Charge.

The German physicist, H. IlelmhoUz, suggested to one of his brilliant

students, Ileinrich Hertz, that he attempt to obtain experimental

proof of Maxwell's theory. Hertz accepted the challenge. His first

problem was to determine whether or not electromagnetic waves

would travel through space without a conductor. While working on

this problem, he observed a tiny discharge between the extremities of

Fig. 258. Apparatus used by Hertz to demonstrate that electric oscillations

produce electromagnetic waves.

a flat coil when a nearby Leyden jar was producing an electric discharge

between two knoblike terminals. This gave him the clue to

the knowledge he was seeking. He produced an oscillating charge by

connecting the terminals of an induction coil, A and 0, to two metal

plates, B and B, which acted as a condenser.

By the simple process of

charging and discharging this condenser, he produced electric oscillations.

That these oscillations really produced electromagnetic waves

he then proceeded to prove by use of a loop of wire, CD, with a small

spark gap. He found that when it was properly oriented sparks jumped

across this gap in the loop of wire at the same instant that they

jumped between the terminals of the induction coil across the room.

The confirmation of Maxwell's electromagnetic theory of radiation

was one of the greatest advances ever made in the realm of physical

science, because it not only presented a principle by which knowledge

of radiant energy could be coordinated, but it paved the way for wireless

telegraphy and the radio.

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