Which of the following is not true about Canal rays?

Correct Answer: D. Do not cause mechanical motion

Canal rays, also known as positive rays, are streams of positively charged ions or cations. These ions are typically produced in a discharge tube when high-speed electrons collide with gas atoms, knocking out electrons from the atoms and leaving behind positively charged ions. Option D is incorrect because canal rays do cause mechanical motion when they collide with other particles or objects due to their kinetic energy. This motion can be used to detect and measure these rays, which was an important experimental technique in early atomic and nuclear physics research. So, option D is not true about canal rays.