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Question

The wavelength of X-rays is of the order of

This question was previously asked in
NDA I 2018 GAT Previous Year Paper (22-Apr-2018)
The correct answer is

1 Å

Understanding X-ray Wavelength

X-rays are a form of electromagnetic radiation, just like visible light, radio waves, and microwaves. These different types of radiation are categorized based on their wavelengths and frequencies. The electromagnetic spectrum is a continuous range of all possible electromagnetic waves.

Electromagnetic Spectrum Overview

The electromagnetic spectrum is ordered by wavelength (or frequency or energy). Starting from the longest wavelengths and lowest frequencies, we have radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Each type of radiation occupies a specific range of wavelengths.

The approximate wavelength ranges for different parts of the spectrum are:

Type of Radiation Wavelength Range (approximate)
Radio Waves > 1 mm to km
Microwaves 1 μm to 1 mm
Infrared 700 nm to 1 μm
Visible Light 400 nm to 700 nm
Ultraviolet 10 nm to 400 nm
X-rays 0.01 nm to 10 nm
Gamma Rays < 0.01 nm

Notice the range for X-rays is from about 0.01 nanometers to 10 nanometers.

Comparing Wavelength Options

The question asks for the order of wavelength of X-rays among the given options. Let's convert the options to a common unit, such as nanometers (nm) or meters (m), to compare them with the typical X-ray wavelength range (0.01 nm to 10 nm, which is \(10^{-11}\) m to \(10^{-8}\) m).

We need to know the conversion factors:

  • 1 Å (Angstrom) = \(10^{-10}\) meters = 0.1 nanometers
  • 1 μm (micrometer) = \(10^{-6}\) meters = 1000 nanometers
  • 1 mm (millimeter) = \(10^{-3}\) meters = \(10^6\) nanometers
  • 1 cm (centimeter) = \(10^{-2}\) meters = \(10^7\) nanometers

Now let's look at the options:

  1. 1 Å: This is equal to 0.1 nm. The X-ray wavelength range is 0.01 nm to 10 nm. 0.1 nm falls within this range.
  2. 1 μm: This is equal to 1000 nm. This is much larger than the typical X-ray wavelength range. This wavelength is in the infrared part of the spectrum.
  3. 1 mm: This is equal to \(10^6\) nm. This is also much larger than the X-ray wavelength range. This wavelength is in the microwave/infrared part of the spectrum.
  4. 1 cm: This is equal to \(10^7\) nm. This is significantly larger than the X-ray wavelength range. This wavelength is in the microwave/radio wave part of the spectrum.

Comparing the values, only 1 Å (0.1 nm) is within the typical range of X-ray wavelengths (0.01 nm to 10 nm). Therefore, the wavelength of X-rays is of the order of 1 Å.

Revision Table: Electromagnetic Spectrum Summary

Radiation Type Approximate Wavelength Range Order of Magnitude
Gamma Rays < 0.01 nm \(10^{-12}\) m and smaller
X-rays 0.01 nm to 10 nm \(10^{-11}\) to \(10^{-8}\) m (order of \(10^{-10}\) m or 1 Å)
Ultraviolet 10 nm to 400 nm \(10^{-8}\) to \(10^{-7}\) m
Visible Light 400 nm to 700 nm \(10^{-7}\) m
Infrared 700 nm to 1 μm \(10^{-7}\) to \(10^{-6}\) m
Microwaves 1 μm to 1 mm \(10^{-6}\) to \(10^{-3}\) m
Radio Waves > 1 mm \(10^{-3}\) m and larger

Additional Information on X-rays

X-rays were discovered by Wilhelm Conrad Röntgen in 1895. They have several important properties and applications:

  • High Energy: X-rays have high energy due to their short wavelengths and high frequencies compared to visible light or radio waves.
  • Penetration: Their high energy allows X-rays to penetrate materials that are opaque to visible light, such as soft tissues in the body. This property is widely used in medical imaging (like bone scans).
  • Ionization: X-rays can ionize atoms and molecules, which is why they can be harmful to living tissue in large doses. This property is used in cancer treatment (radiation therapy).
  • Production: X-rays are typically produced when high-speed electrons collide with a metal target. The sudden deceleration of electrons produces continuous X-rays (Bremsstrahlung), and electron transitions within the target atoms produce characteristic X-rays.
  • Applications: Besides medical imaging and therapy, X-rays are used in material analysis (X-ray diffraction), security screening, and astronomy (to study high-energy phenomena).
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Similar Questions

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Important Questions from Electromagnetic Waves

  1. The radio waves used for signaling and communication can be classified as which of the following?

  2. An electromagnetic wave propagates through a transparent, non-magnetic medium. If the relative permittivity of this medium is $\epsilon_r = 4$, and its relative permeability is $\mu_r = 1$, what is the speed of the electromagnetic wave in this medium? (Assume the speed of light in vacuum is $c = 3 \times 10^8$ m/s).
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