Wavelength or Frequency determines the color of light

There is a question in test 2 below,
An architect is specifying the light fixtures for a small retail shop. The client is concerned about the color of the light sources.

Which of the following determines the color of light?


Correct. The wavelength of light determines its color. The visible light spectrum ranges from red (longest wavelength) to violet (shortest wavelength).


Incorrect. Phase changes can occur in light as it is reflected, but this does not impact color in a way that can be utilized when selecting light fixtures.


Incorrect. Frequency and wavelength are closely related, but the wavelength of light determines its color.

Isn’t the speed of light (299 792 458 m / s in our universe) equals to frequency times wavelength? Redlight has longer wavelengh - smaller frequncy and purplelight has shorter wavelength - larger frequency. It’s very confusing to me for the explanation of choice ‘Frequency’ since I think both frequency and wavelength could determine color of light. I don’t think this is a good question.

Hi @jiacheng !

Thanks so much for your question! I’m going to tag @coachchrishopstock so he can address your concerns regarding this question and the answer explanations. Thank you again!


Hi @jiacheng thanks for writing in! According to the reference for this question, Mechanical and Electrical equipment for buildings (page 177 and figure 6.1) wavelength is said to be the determining factor for the color of light. I see what you’re saying about frequency and wavelength being proportional, but it’s important to remember for the ARE that each question is written according to a specific reference that’s listed in the Handbook. I think it’s also more common to say that wavelength determines frequency.
I hope this was helpful and good luck on your next exam!