BharatNotes Diffraction
nounUsage in a UPSC answer
Just as light undergoes diffraction when it strikes the edge of an obstacle and bends into the shadow, a well-designed welfare scheme can diffract benefits around bureaucratic obstructions to reach citizens in the remotest periphery, ensuring that no eligible household is left in administrative darkness.
Synonyms
Antonyms
Word Family
diffract (v), diffractive (adj), diffractively (adv), diffractometer (n)
Root
Latin diffringere = to break into pieces; dis- = apart + frangere = to break; noun diffractiō
Etymology
From Latin diffringere ("to break into pieces"), from dis- ("apart") + frangere ("to break"); coined by Francesco Maria Grimaldi in the 17th century.
Memory Hook
DIFFRACTION = "di-FRACT-ion" — think of a FRACTURE (Latin frangere, "to break"): a wave is broken apart and bent as it squeezes past an edge, so its path FRACTURES and spreads.
How This Word Works in UPSC Writing
The spreading of a wave as it passes an obstacle or through an aperture, without any change of medium. The governing condition is the one that explains everything else: diffraction is appreciable only when the obstacle or opening is comparable in size to the wavelength. Sound has wavelengths of the order of metres, so it bends readily around a doorway, while visible light has wavelengths of a few hundred nanometres and does not, which is precisely why a person around a corner can be heard but not seen. Two consequences matter. Diffraction sets the ultimate resolution limit of every optical instrument, so a telescope's resolving power improves with the diameter of its aperture rather than with magnification. And X-ray diffraction reveals crystal structure because X-ray wavelengths happen to match the spacing between atoms, which is how the structure of DNA and of countless minerals was determined.
Don’t Confuse It With
Diffraction is bending around an obstacle or through an aperture and requires no change of medium. Refraction is bending caused by a change in speed on entering a new medium, so the underlying cause is different. Scattering is redirection by small particles and is what makes the sky blue. Interference is the superposition of waves, and a diffraction pattern is in fact produced by interference between different parts of the same wavefront. Dispersion is separation of a wave into its component wavelengths.
Hindi Meaning
विवर्तन (vivartan).
Common Questions
- What is diffraction?
- The spreading and bending of waves as they pass through an aperture or around the edge of an obstacle.
- Why can we hear around a corner but not see around it?
- Because diffraction is significant only when the obstacle is comparable to the wavelength, and sound waves are metres long while light waves are a few hundred nanometres.
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