Final answer:
A photodetector measures the intensity of the specific wavelength of interest, rather than the length of light waves, enzyme activity, analyte concentration, or the speed of light transmittance.
Step-by-step explanation:
A photodetector is an instrument designed to measure various properties of light. When considering the options provided in the student’s question, a photodetector chiefly measures the intensity of the specific wavelength of interest. It does not measure the length of light waves, enzyme activity, analyte concentration, nor the speed of light transmittance. Instead, detectors such as photomultiplier tubes, CCD cameras, and photographic plates are sensitive to the intensity of the light, which is related to the number of photons interacting with the detector. In instruments like spectrometers and spectrophotometers, photodetectors are essential for recording and measuring the spectrum and properties of light after it has been sorted by wavelength or passed through a filter.