Short Answer
More slits → interference sharper (resolving power ∝ N × m) is the best answer.
Wave and optics questions test how frequency, wavelength, phase, interference, and geometry fit together. Start with the physical picture before choosing the equation.
Resolving power R = mN (order × number of slits): with N slits, peaks become narrower and brighter, improving spectral resolution.
Why This Answer Is Correct
This is a Hard-level question in Waves & Optics. The prompt is really testing whether you can connect the concept to its defining physical relationship instead of picking a nearby-but-wrong term.
If a waves question feels messy, sketch the geometry or phase relationship first, then return to the algebra.
Choices At A Glance
- A. Grating has fewer slits
- B. More slits → interference sharper (resolving power ∝ N × m)
- C. Grating reflects, double-slit transmits
- D. Grating separates colours by refraction
When similar options appear on an exam, eliminate the ones that break the core law, use the wrong units, or confuse a definition with a consequence.
Topic Snapshot
Topic: Waves & Optics
Difficulty: Hard
Best next move: Re-state the governing law in your own words, then solve one more example from the same topic before moving on.