Q20
General SciencePhysics
The range of visible spectrum is
- a.350 - 650 nm
- b.380 - 750 nm
- c.390 - 700 nm
- d.400 - 800 nm
No option is correct as printed — this question is disputed. WBPSC awarded the mark to all candidates: two options (B) 380–750 nm and (C) 390–700 nm are both standard textbook ranges for the visible spectrum.
The question has more than one defensible answer: the limits of visible light are quoted variously as about 380–750 nm and about 390–700 nm (roughly 400–700 nm), so both (B) and (C) appear in standard books. The PSC therefore awarded the mark to all candidates.