Which one of the following statements about X-rays is not true ?

Option C is incorrect because radar systems utilize Radio waves or Microwaves, not X-rays. Radar relies on waves with longer wavelengths that can travel long distances and reflect off objects without being significantly absorbed by the atmosphere.

• Statement A: X-rays typically have wavelengths in the range of 0.01 to 10 nanometers; 1 Å (0.1 nm) falls squarely within this spectrum.
• Statement B: X-rays are generated when high-velocity electrons are decelerated upon hitting a metal target (Bremsstrahlung) or by knocking out inner-shell electrons of the target atoms.
• Statement D: In medical science, high-energy X-rays (radiotherapy) are used to destroy malignant cancer cells by damaging their genetic material.

Since X-rays are highly ionizing and have high penetrative power, they would be absorbed or pass through objects rather than reflecting back to a receiver, making them unsuitable for radar.