How do x-rays pass through some materials but not others?
Quick Answer
X-rays are absorbed more by dense materials and materials with higher atomic numbers, such as bone or metal. Softer tissues let more x-rays pass through.
The Full Story
X-rays are high-energy electromagnetic waves discovered by Wilhelm Conrad Röntgen in 1895. When they pass through matter, some photons are absorbed or scattered depending on the material’s thickness, density, and atomic composition. Bone appears white on an x-ray image because calcium-rich tissue absorbs more x-rays than surrounding soft tissue. Metal absorbs even more strongly, which is why it shows up very clearly. This differential absorption is what allows medical imaging and airport security scanners to form pictures of hidden structures.
Key Facts
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"Why bones show up so clearly on x-rays"