Question

a scientist wants to study how different materials absorb ultraviolet light. why cant they use their eyes to directly observe this process?
human eyes can only see ultraviolet light in complete darkness
ultraviolet light moves too fast for human eyes to track
ultraviolet light is too bright for human eyes to safely observe
human eyes cannot detect ultraviolet wavelengths, so special instruments are needed

Explanation:

The visible spectrum for human eyes is limited. Ultraviolet light has wavelengths outside the range that human eyes can detect. Special instruments are required to study ultraviolet light as they can detect these non - visible wavelengths. The first option is incorrect because even in darkness, human eyes can't see ultraviolet light. The second option about speed is not relevant to detection by eyes. The third option about brightness is also not the reason (it's about wavelength detectability, not just brightness).

Answer:

Human eyes cannot detect ultraviolet wavelengths, so special instruments are needed.