Physics – Electromagnetic Spectrum (X-rays) What is the typical order of magnitude of the wavelength of X-rays used in physics and medical imaging? Choose the closest standard value.

Introduction / Context:
X-rays are high-energy electromagnetic waves widely used in medical radiography, crystallography, and materials testing. This question checks whether you know the correct order of magnitude of their wavelength, which helps distinguish X-rays from ultraviolet light and gamma rays in the electromagnetic spectrum.

Given Data / Assumptions:

• X-rays lie between ultraviolet and gamma rays in frequency/energy.
• Typical diagnostic and diffraction X-rays have very short wavelengths.
• We must select the closest standard order of magnitude.

Concept / Approach:
Electromagnetic spectrum regions are often identified by wavelength bands. X-rays commonly used in crystallography (Cu Kα, Mo Kα) have wavelengths on the order of 1 angstrom (1 Å = 10^-10 m). Medical X-ray tubes produce a spectrum with effective wavelengths in the sub-nanometre range, again of angstrom order. Values like centimetres or metres belong to radio/microwave, and microns (micrometres) correspond to infrared, not X-rays.

Step-by-Step Solution:

Verification / Alternative check:
Energy–wavelength relation: E = hc / λ. X-ray photon energies in keV imply λ in Å. For example, 12.4 keV corresponds roughly to 1 Å using hc ≈ 12.4 keV*Å. This matches the angstrom scale and validates the choice.

Why Other Options Are Wrong:

• 10 micron: Infrared radiation, much longer than X-rays.
• 1 cm: Microwave band.
• 1 m: Radio waves.

Common Pitfalls:
Confusing nanometres and angstroms. Note that 0.1 nm = 1 Å; many X-ray problems quote λ in Å because crystal interplanar spacings are of similar size, enabling diffraction (Bragg’s law).

Final Answer:
1 angstrom