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General ScienceMediumAsked in: NDA · NDA-II 2022, GAT

Which one of the following wavelengths corresponds to the wavelength of X-rays?

  1. A.500 nm
  2. B.5000 nm
  3. C.100 nm
  4. D.1 nm

Correct answer

D. 1 nm

Explanation

The correct answer is D, 1 nm. X-rays have wavelengths of roughly 0.01 nm to 10 nm, so 1 nm sits right inside the X-ray band.

The electromagnetic spectrum runs, from the shortest wavelength to the longest, as gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves and radio waves. Visible light covers only about 400 nm (violet) to 700 nm (red). X-rays are far shorter than this, which gives them high energy and lets them pass through soft tissue but not bone; that is why they are used in radiography. They were discovered by Wilhelm Röntgen in 1895.

A is wrong because 500 nm is visible light, in the blue-green part of the spectrum.

B is wrong because 5000 nm, or 5 micrometres, lies in the infrared region that we feel as heat.

C is wrong because 100 nm lies in the ultraviolet region, between visible light and X-rays.

Exam tip: gamma < X-ray < UV < visible (400–700 nm) < infrared < microwave < radio, in order of wavelength.

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Practice Questions

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Q3.General ScienceAsked in: CDS · CDS-II 2022, GKEasy

Deficiency of iron causes

  1. A.Anaemia
  2. B.Scurvy
  3. C.Rickets
  4. D.Cholera
Show answer
Correct answer: A. Anaemia

Iron is needed to make haemoglobin, so too little iron means too little haemoglobin and a reduced ability of the blood to carry oxygen.

Q4.General ScienceAsked in: CDS · CDS-I 2026, GKMedium

Consider the following statements regarding waves : 1. If the particles of a medium move along the direction of motion of the wave, the wave is called a longitudinal wave. 2. If the particles of a medium move perpendicular to the direction of motion of the wave, the wave is called a transverse wave. 3. Transverse waves may involve change in the shape of the medium, whereas longitudinal waves involve change in the density of the medium. Which of the statements given above is/are correct ?

  1. A.1 and 2 only
  2. B.1 only
  3. C.2 and 3 only
  4. D.1, 2 and 3
Show answer
Correct answer: D. 1, 2 and 3

All three statements correctly describe how particles move in the two kinds of mechanical waves. In a longitudinal wave, such as sound in air, the particles vibrate back and forth along the direction in which the wave travels.