Question

What are X-rays ? How are they produced ? Give two uses of X-rays.

Hint:

Minimum wavelength of continuous X-rays depends only on accelerating potential $V$: $\lambda_{min} = \frac{hc}{eV} \approx \frac{12400}{V\text{ (in Volts)}}\text{ \AA}$.

Answer 1

Concept:
• X-rays are high-energy electromagnetic radiations with very short wavelengths ranging from approximately $0.01\text{ nm}$ to $10\text{ nm}$ ($10^{-11}\text{ m}$ to $10^{-8}\text{ m}$).

Step 1: Definition of X-rays
X-rays are energetic, invisible electromagnetic waves located in the spectrum between ultraviolet rays and gamma rays, characterized by high frequencies ($\approx 10^{16}\text{ Hz}$ to $10^{19}\text{ Hz}$) and strong penetrating power through matter.

Step 2: Production Mechanism
X-rays are produced in a Coolidge tube when high-speed energetic electrons emitted from a heated filament are accelerated through a high potential difference ($\approx 10\text{ kV}$ to $100\text{ kV}$) and suddenly decelerated upon striking a heavy metal target (like Tungsten or Molybdenum) of high atomic number and high melting point.
The loss of kinetic energy of fast-moving electrons during sudden deceleration produces continuous X-rays (Bremsstrahlung or braking radiation), while inner-shell atomic transitions in the target produce characteristic X-rays.

Step 3: Two Uses of X-rays
1. Medical Diagnostics and Therapy: Used in radiography (X-ray imaging) to detect bone fractures, foreign metallic objects, dental cavities, and in radiation therapy to destroy malignant cancer tumors.
2. Industrial and Scientific Applications: Used in crystallography for analyzing crystal structures via X-ray diffraction, and in industrial quality control to inspect internal defects, cracks, and welds in metal castings.

Step 4: Conclusion
X-rays are short-wavelength electromagnetic waves generated by decelerating fast electrons against a metallic target, widely applied in medical imaging and structural crystal analysis.