Answer:
Explanation:
1) Wavelengths for the different light colors (visible light) and related character:
Color Wavelength related character
Violet 380–450 nm ← Professr Plum
Blue 450–485 nm ← Mrs. Peacock
Cyan 485–500 nm
Green 500–565 nm ← Mr. Green
Yellow 565–590 nm ← Colonel Mustard
Orange 590–625 nm
Red 625–740 nm ← Miss Scarlet
2) At the time of the murder, the spectrometers recorded:
a) In the dining room: 520 nm.
520 nm is in the range 500 - 565 nm, which is the range for green color, so Mr. Green was in the dining room and is no more a suspect.
b) In the lounge and study: lower frequencies.
Since frequency and wavelength are inversely related, the wavelengths in the longe and study have to be of yellow and red colors, which are the only two with longer wavelengths from the option given.
Then, Mustard and Scarlet are not criminal.
c) In the library: the second shortest wavelength of the five recorded.
The second shortest wavelength, as per the table, is that of blue color. So, Mrs. Peacock is not the killer.
The only left option is violet, so Mr. Plum is the only who could be at the conservatory and he is the killer.