by Sarah Scoles
Sensibly, we think of light as something we can see, because light is how we see (although, as I will discuss later, even this idea is not intuitive). But that view of light neglects most of the electromagnetic spectrum.
This month, the Astronomy Education Review published an article by Libarkin, et al., about students', and teachers' misconceptions about light--both visible light and higher- and lower-energy light (such as infrared and ultraviolent) that are invisible to our narrow-minded eye-lenses.
As I have discussed previously, anything made of photons is light. This includes radio waves, microwaves, visible light, infrared radiation, ultraviolet rays, X-rays, and gamma rays. Just because our eyes are not 200-feet across and we can't see radio waves does not mean that they are not, fundamentally, the same phenomenon as the light that comes out of your lamp.
However, many students and teachers (and clerks and historians and brewmasters and dogs) don't think about light as including the invisible electromagnetic radiation. And that makes sense. After all, you don't often encounter a situation in which your interaction with the world would change if you knew more about the photons zipping around you.
What are the common misconceptions?
Let me start by saying that most misconceptions about light are based on semi-logical, commonsense interpretations of experiences. In this study, a student believed that cats' eyes could be seen in complete darkness, because they had seen cats' eyes in, for example, a dark basement. However, they could see the cats' creepy eyes because of ambient light coming from the warm, welcoming, uncreepy upstairs.
- only came from the Sun
- would allow them to see objects if it were shone on them
- was not an electromagnetic wave
- they didn't really know what it was at all
- they didn't know why "red" was in the name
Why is it important to know that light is light is light?Because then you possess a more full understanding of the universe, of course. And you will be a happier and more fulfilled person.
Actually, it's important because most of the light spectrum is not visible, and many interesting processes that occur in the universe are completely invisible to your pathetic eye-holes. If students don't understand that the X-rays shot out from the accretion disks of black holes are basically the same as their car's headlights, but with more energy, that signals that they do not understand what any kind of light truly is--not just that they don't understand what invisible light is.
Astronomy, and chemistry and physics and biology, all require an understanding of the different flavors of photons. To think only of visible light as "light," and not to really understand what "light" is, is pretty discriminatory, and this is the twenty-first century, and we have laws against that.
Let's get some action items: What needs to be done?
In order for commonsense misconceptions, which have a firm mental footing, to be dispelled, they have to be confronted directly. That's why studies such as this one are important: you can't address misconceptions if you don't know what they are. False ideas about light will only change if correct ideas are not only presented, but presented in a convincing, inquiry-based way that allows students to reconstruct their worldview to fit the new evidence. Simply saying, "Yo, X-rays are photons, too," is not enough and will not be incorporated into life after the midterm.
Libarkin, J., Anila, A., Crockett, C., Sadler, P. (2011). Invisible Misconceptions: Student Understanding of Ultraviolet and Infrared Radiation. Astronomy Education Review. 10(1).
Libarkin, J., Asghar, A., Crockett, C., & Sadler, P. (2011). Invisible Misconceptions: Student Understanding of Ultraviolet and Infrared Radiation Astronomy Education Review, 10 (1) DOI: 10.3847/AER2011022