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<span>The longest wavelength within the visible spectrum is the red
light. The answer is letter C. It is called visible light because it is the
only light that can be seen by the human eye. Red light is the longest
wavelength around 620 to 750 nanometer. It is followed by orange which has a
wavelength of 590 t 620 nanometer. And then blue which has a wavelength of 450
to 495 nanometer. And the shortest wavelength is violet which has a wavelength
of 380 to 459 nanometer. </span>
