My speculation is that this is the L&C logic: In math, adding a positive and a negative number with the same absolute values gives a sum of zero. In chemistry, acids can neutralize alkalis and vice versa. By analogy, light with lower frequency than is visible to the human eye will cancel out the effects of light with a higher than visible frequency.
I am not an expert in the electromagnetic spectrum or how it affects the human anatomy, but I certainly wouldn't try that experiment! My understanding is that the analogy is flawed and another example of the show playing fast and loose with science in the interests of plot progression.
Joy,
Lynn
