CURVED LINE SOURCE 



27 



The directional characteristics for an arc of 60°, 90° and 120° are shown 

 in Figs. 2.4, 2.5 and 2.6. The interesting feature of the directional char- 



RADIUS - X 



RADIUS =2X 



Fig. 2.4. Directional characteristics of a 60° arc as a function of the radius and the wave- 

 length. The polar graph depicts the pressure, at a large fixed distance, as a function of the 

 angle in the plane of the arc. The pressure for the angle 0° is arbitrarily chosen as unity. 



acteristics of an arc is that the directional characteristics are very broad 

 for wavelengths large compared to the dimensions, and are narrow for 



RADIUS = •=■ 



RADWS- 



RADIUS' 2X 



Fig. 2.5. Directional characteristics of a 90° arc as a function of the radius and the wave- 

 length. The polar graph depicts the pressure at a large fixed distance, as a function of the 

 angle in the plane of the arc. The pressure for the angle 0° is arbitrarily chosen as unity. 



wavelengths comparable to the dimensions and are broad again for wave- 

 lengths small compared to the dimensions of the arc. The arc must be 



