________________
Explanation. The high potential difference across the metal plates ionises the air between the sphers S, and S, and allows a path for discharge of plates. During the discharge of plats, a sparks is produced between the spheres due to the high potential difference. (= 5 x 10' Hz). It results in oscillations of charges on the plates at such a high frequency. Therefore, a highly ascillating electricfied is produced acrass the vertical gap between the tow sphers. It, in turn, produces a highly oscillating magnetic field of same frequency in horizontal plane and perpendicular to the gap between the spheres. The oscillating electric and magnetic fields constitute electromagnetic waves of the same frequency ( 5 x 107 Hz.) and these waves are radiated from the spark gap." Text-book of Physics (Std. XII), part II, Pages 95-97– Here, Q, and Q, are two metallic spheres. Joined to them are two metallic rods M and N with some space between called spark gap S. The rods are connected to the two terminals of an induction coil to provide high intermittant voltage. The spheres Q, and Q, act as capacitors and the rods acts as inductors. This arrangement threfore, acts as an oscillagling circuit in which atternately Q, and Q, acquire positive and negative charges which reverse in their polarity each time a spark passes across the gap S. The process repeats itself rapidly with a difinite period. The electromagnetic waves generated in the process are detected by another spark gap arrangement R placed at some distance from
235
Jain Educationa International
For Personal and Private Use Only
www.jainelibrary.org
