A monochromatic source of light operating at 15 kW emits 2.5×10²² photons/s. The region of an electromagnetic spectrum to which the emitted electromagnetic radiation belongs is (Take h=6.6×10⁻³⁴ J s and c=3×10⁸ m/s)

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(4) Ultraviolet. E=P/n=(1.5×10⁴)/(2.5×10²²)=6×10⁻¹⁹ J. 
u=E/h=(6×10⁻¹⁹)/(6.6×10⁻³⁴)=9.1×10¹⁴ Hz. λ=c/u=(3×10⁸)/(9.1×10¹⁴)=3.3×10⁻⁷ m =330 nm. That is shorter than the 400 nm violet edge, so the radiation is ultraviolet.

A monochromatic source of light operating at 15 kW emits 2.5×10²² photons/s. The region of an electromagnetic spectrum to which the emitted electromagnetic radiation belongs is ______ (Take h=6.6×10⁻³⁴ J s and c=3×10⁸ m/s)

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Why the other options are wrong