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Asked in GUJCET 2023 · Ranges, production and detection
Idea: convert the wavelength limits of visible light with u = c/λ.
Visible light runs from about λ = 700 nm at the red end to about λ = 400 nm at the violet end.
Red: u = (3×10⁸)/(7×10⁻⁷) = 4.3×10¹⁴ Hz, i.e. roughly 400 THz.
Violet: u = (3×10⁸)/(4×10⁻⁷) = 7.5×10¹⁴ Hz, i.e. roughly 700 THz.
Since 1 THz = 10¹² Hz, the range is 400 THz to 700 THz.
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