Claudia, Argentina asked:
When I was younger I was told not to sit too close to the TV. Is it an urban myth that it's dangerous to sit too close? Or does the TV emit radiation? Does this still apply to modern televisions?
We put this question to Andy Karam, adjunct professor at the Rochester Institute of Technology...
Andy - Televisions really do give off radiation. But having said that, itís only a little bit of radiation and itís not that dangerous. What happens is that anything with a cathode ray tube, a tube where you shoot high-energy electrons at some sort of screen, when those electrons hit the screen, they give off very low energy x-ray radiation. This is the same way that x-rays are produced in regular x-ray tubes. So, if you're sitting close to a cathode ray tube, whether a computer monitor, a television screen, a radar set or anything else with that type of technology, you're going to be getting low doses of x-ray radiation.
Now having said that, Iíve got to emphasize, they're low doses of radiation. Itís not enough to be dangerous and in fact, if you watch your television for several hours a day all year, you're getting less radiation than you would from a single medical x-ray and less radiation than you get from the radioactivity thatís just naturally within your body. So, itís something that we can measure, but itís not something thatís harmful.
LCD and plasma screens don't give off any radiation at all. They don't use high-energy electrons. Itís a different type of technology. I could not say that they're safer because I don't consider the radiation from cathode ray tubes to be a risk, but I can say that they give off less radiation. As far as sitting too close to the television goes, the further back you are, the lower the radiation dose will be. But having said that, I don't consider the radiation dose even at a distance of just one metre to be dangerous.
Part of the show Why does Water Expand when it Freezes? from the 11th Oct 2009
If you sit too close you block the grown-up's view.
TV sets presumably have to conform to industrial standards nowadays, that they emit minimal radiation.
I was told the same thing also but that was in the 1960's.
Urban Myth.. possibly stemming from a *little* truth. I agree with the mad man (never thought I'd be uttering those words again - sheesh!) it's less to prevent eyes damage and more eye strain.
I always thought that CRTs emitted x-rays (albeit at low intensity) and this was the reason not to sit too close, so as to reduce the dose. But then again, unless they are coming off at very wide angles, the distance from the TV wouldn't make an enormous different to your dose would it, air not posing much of a barrier to an x-ray... chris, Wed, 7th Oct 2009
"TV's now have LCD screens ... and emit no radiation. "
I don't know about X-rays, but there is another good reason why you should not spend a long time staring at anything from a short distance, especially as a kid. This has something to do with the development of the eyeballs and short sightedness. A child's eyes are smaller than an adult's, therefore they have to grow as one reaches adulthood. During this growth period, it is important to keep an appropriate shape and size, so that the picture projected onto the retina by lens is sharp. The exact mechanism is still unclear, but it appears, that it has something to do with the relaxed state of the lens. When you look in the distance (infinity) your lens is relaxed. If you need to "focus" to look in the distance, it tells your body: "Your eyeballs are too small". So there is a growth response to distance the retina a bit farther away from the lens. This mechanism must have served really well in our evolutionary past, because humans looked in the distance quite often. But in the age of book printing, TV and the Internet it is not working that well at all. During growth we are staring at a monitor, and therefore our eyes are getting a lot of growth signals. So if you keep a distance from the TV it may help to prevent short sightedness. Or at least helps to have a less severe one.