Chemistry · Structure Of Atom · NEET
Wilhelm Conrad Roentgen (a German physicist) discovered X-rays in 1895. He was working with a cathode ray (discharge) tube. When the fast electrons hit the metal part of the tube, an unknown ray came out that made a nearby screen glow, even though the tube was covered. He named it 'X-ray' because X stands for an unknown quantity.
X-rays are NOT particles like electrons. They are electromagnetic waves, the same family as visible light and radio waves, but with a much shorter wavelength (about 0.01 to 10 nanometres). Cathode rays are streams of electrons; X-rays are the high-energy light produced WHEN those electrons crash into metal and stop suddenly.
No. X-rays have no charge and no mass. Because they are neutral electromagnetic waves, they are NOT bent (deflected) by electric fields or magnetic fields. This is a key point that separates them from cathode rays (negative) and anode/canal rays (positive).
Cathode rays are fast-moving electrons; they have negative charge and mass, and they bend in electric and magnetic fields. X-rays are electromagnetic waves; they have no charge, no mass, and do not bend in these fields. Cathode rays are the CAUSE, X-rays are the RESULT: X-rays form when cathode rays hit a metal target (like the anode).
X-rays have high energy and short wavelength, so they can pass through low-density material like skin and muscle. Denser material like bone or metal absorbs more X-rays and blocks them. This is why bones show up white (blocked rays) and soft tissue looks dark on a medical X-ray photograph.
They are both high-energy electromagnetic waves with very short wavelengths and no charge, and they overlap. The usual difference is their SOURCE, not their nature: X-rays come from electrons hitting metal (outside the nucleus), while gamma rays come from inside the nucleus during radioactive decay. Gamma rays are generally even more energetic.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Yes. X-rays belong to the electromagnetic spectrum, just like visible light. The only difference is the wavelength: X-rays have a much shorter wavelength and much higher energy than visible light, so our eyes cannot see them.
Yes. Because X-rays are electromagnetic waves, they travel through vacuum at the speed of light, about 3 x 10^8 metres per second, the same as all other EM waves.
X-rays are usually taught as background to the discharge tube experiments (cathode rays, canal rays). NEET mostly tests X-rays as a comparison point: knowing they are chargeless EM waves helps you answer 'which ray is not deflected' type questions.
Yes. X-rays carry enough energy to knock electrons out of atoms, so they are called ionising radiation. This is why long exposure can harm living cells, and why they are handled carefully in hospitals.
