Q.X-rays were discovered by ________ in 1895.
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X-rays were discovered by W. C. Rontgen in 1895 while studying cathode rays (a stream of electrons emitted from the cathode of a vacuum tube), and are also called Rontgen rays after him. They are produced when a beam of cathode-ray electrons is suddenly stopped by striking an obstacle or target of high atomic number, such as molybdenum or copper.
Because X-ray photons carry very high energy, X-rays have a high penetrating power, able to pass through several centimetres of solid matter, which allows them to visualise the interior of objects that are opaque to ordinary visible light. Along with ultraviolet and gamma rays, X-rays belong to the class of ionizing radiation: they carry enough energy to strip electrons from atoms and molecules lying along their path, turning them into ions, and this ionizing ability is precisely what makes an overdose of …
X-rays are short-wavelength, highly penetrating electromagnetic radiation, first noticed as an unexplained glow on a covered fluorescent screen kept near a …
X-rays were discovered by Wilhelm Conrad Röntgen in 1895 while experimenting with cathode-ray (discharge) tubes, for which he received the first-ever Nobel Prize in Physics (1901).
Röntgen noticed that a fluorescent screen kept some distance from a discharge tube (covered in black paper so no visible or cathode-ray light could escape) still glowed, revealing an unknown, highly penetrating radiation that he called 'X-rays' because their nature was then unknown.
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- CBSE 2025Set D1 markMCQQ.X-rays are (A) moving electron (B) moving positive ions (C) moving negative ion (D) electromagnetic waves
›Reveal solutionSolution
X-rays are electromagnetic waves of very short wavelength.
X-rays are produced when fast electrons are suddenly decelerated on striking a metal target, but the X-rays themselves are electromagnetic radiation — transverse waves of oscillating electric and magnetic fields travelling at the speed of light. Their wavelength (about 0.01–10 nm) is much shorter …
- CBSE 2024Set ANNUAL1 markQ.What electromagnetic waves are used to examine the crystal structure of solids?
›Reveal solutionSolution
X-rays are used to examine crystal structure because their wavelength matches the spacing between atomic planes in a crystal, producing a measurable diffraction pattern.
X-rays have wavelengths of the order of 0.1-1 Angstrom (10^-11 to 10^-10 m), comparable to the spacing between atomic planes in a crystal lattice. When X-rays are incident on a crystal, they get diffracted by the regularly-spaced atoms according to Bragg's law, 2dsinθ=nλ, producing a diffraction pattern that reveals the crystal's internal atomic arrangement. Th …
- CBSE 2023Set F1 markMCQQ.X-rays are (A) moving electron (B) moving positive ion (C) moving negative ion (D) electromagnetic waves
›Reveal solutionSolution
X-rays are electromagnetic waves of very short wavelength.
X-rays are electromagnetic radiation with wavelengths of about 0.01–10 nm (frequency ~1016–1019 Hz), lying between ultraviolet and gamma rays in the electromagnetic spectrum. They are not streams of charged particles; they are uncharged, travel at the speed of light in vac …
- CBSE 2023Set ANNUAL1 markMCQQ.X-rays were discovered by ________ in 1895.(a) Roentgen(b) J.J. Thompson(c) William Crookes(d) Rutherford
›Reveal solutionSolution
X-rays were discovered by Wilhelm Conrad Röntgen in 1895 while experimenting with cathode-ray (discharge) tubes, for which he received the first-ever Nobel Prize in Physics (1901).
Röntgen noticed that a fluorescent screen kept some distance from a discharge tube (covered in black paper so no visible or cathode-ray light could escape) still glowed, revealing an unknown, highly penetrating radiation that he called 'X-rays' because their nature was then unknown.
…
- CBSE 2022Set M1 markQ.Name the type of electromagnetic rays lying between ultraviolet and gamma rays.
›Reveal solutionSolution
Between UV and gamma rays lie X-rays.
Arranging the electromagnetic spectrum in order of increasing frequency (decreasing wavelength): radio waves → microwaves → infrared → visible → ultraviolet → X-rays → gamma rays. …
- CBSE 2020Set 55/2/11 markMCQQ.Electromagnetic waves used as a diagnostic tool in medicine are (A) X-rays. (B) ultraviolet rays. (C) infrared radiation. (D) ultrasonic waves.
›Reveal solutionSolution
The question asks which electromagnetic wave is used as a diagnostic tool in medicine. X-rays are the correct choice because they penetrate soft tissue but are absorbed by denser materials like bone, making them ideal for imaging fractures and internal structures. The answer is (A) X-rays.
Let’s start with the core idea. The question is about electromagnetic waves used in medical diagnostics. The key is to distinguish between the different types of electromagnetic radiation and their specific applications in medicine. Not all EM waves are suitable for imaging inside the body — some are absorbed too quickly, some don’t penetrate at all, and others are used for therapy rather than diagnosis.
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What does “diagnostic tool” mean here?
In medicine, a diagnostic tool helps visualize internal structures or detect abnormalities without surgery. The most common example is an X-ray image of a broken bone. The wave must be able to pass through the body (penetrate) and then be detected on the other side, with different tissues absorbing different amounts.
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Consider each option:
- (A) X-rays: These have very short wavelengths (10−11 to 10−8 m) and high energy. They penetrate soft tissues (skin, muscle) but are absorbed by denser materials like bone. This differential absorption creates a shadow image on a detector — that’s a radiograph. X-rays are the backbone of diagnostic radiology.
- (B) Ultraviolet rays: UV has shorter wavelengths than visible light (10−8 to 10−7 m) and is mostly absorbed by the skin’s outer layers. It causes sunburn and can damage DNA, but it does not penetrate deep enough to image internal organs. UV is used in sterilization or treating skin conditions, not for internal diagnostics.
- (C) Infrared radiation: IR has longer wavelengths (10−3 to 10−6 m) and is felt as heat. It penetrates only a few millimeters into the skin. While thermal imaging (thermography) can detect surface temperature patterns, it is not a primary diagnostic tool for internal structures like bones or organs.
- (D) Ultrasonic waves: These are not electromagnetic waves — they are mechanical sound waves with frequencies above human hearing. Ultrasound is indeed a diagnostic tool (e.g., fetal imaging), but the question specifically asks for electromagnetic waves. So this option is out.
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Why not UV or IR?
Both UV and IR are electromagnetic, but their penetration depth in human tissue is too shallow for imaging deep structures. UV is absorbed by the epidermis; IR is absorbed by water in tissues within a few millimeters. Only X-rays have the combination of high energy and low absorption in soft tissue to create useful internal images. …
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- CBSE 2018Set ANNUAL1 markQ.Name the part of electromagnetic waves which is used in radiography?
›Reveal solutionSolution
Radiography uses X-rays, the high-frequency, short-wavelength part of the electromagnetic spectrum.
The electromagnetic spectrum contains, in order of increasing frequency (decreasing wavelength): radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and γ-rays. X-rays have wavelengths roughly in the range 10−8 m to 10−13 m and correspondingly very high photon energies. This gives them strong penetrating power through soft materials (flesh, cloth) while being significantly absorbed by denser materials (bones, metals). This …
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