Case: Read the passage and answer the question.
The electromagnetic (EM) spectrum is the range of all types of EM radiation. Radiation is energy that travels and spreads out as it goes – the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic radiation. The other types of EM radiation that make up the electromagnetic spectrum are microwaves, infrared light, ultraviolet rays, X-rays and gamma rays.
Which of the following is one common way of producing X-rays?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Bombardment of a metal target by high-energy electrons
Each band of the electromagnetic spectrum is classified roughly by how its waves are produced and detected. So every source in the options belongs to one particular band.
Option (1) Radioactive decay of the nucleus — Incorrect. Radioactive nuclei emit gamma rays, the band of still shorter wavelength (below about \( 10^{-3}\,\mathrm{nm} \)) beyond the X-rays.
Option (2) Vibration of atoms — Incorrect. Vibrating atoms radiate infrared waves, of wavelength 1 mm to 700 nm, far longer than X-rays.
Option (3) Vibration of molecules — Incorrect. Molecular vibrations in hot bodies give out infrared (heat) waves. These waves carry far too little energy to produce X-rays.
Option (4) Bombardment of a metal target by high-energy electrons — Correct. In an X-ray tube, electrons accelerated to high energy strike a metal target and are stopped suddenly. This rapid deceleration of the charges gives out X-rays, of wavelength about 10 nm down to \( 10^{-4}\,\mathrm{nm} \).
NCERT (2026-27):
X-rays – “Beyond the UV region of the electromagnetic spectrum lies the X-ray region. … One common way to generate X-rays is to bombard a metal target by high energy electrons.”