Is light invisible??

If light is invisible and is only visible if someone is there to observe it, then how are people still able to get suntans on sunbeds? When a person lays on a sunbed they have to wear eye protection to block out the light and some people even fall asleep while getting their tans. If they are the only person in the room while the light from the sunbed is hitting their skin and they are asleep while this is happening so they do not observe any light, how come they still have a suntan when they wake up?

Wut? Are you saying if something has an effect then it must be visible?

You're confusing yourself with "tree falling in the woods" issues. That's totally irrelevant to your question.

Ultraviolet light, which is what's used in tanning beds, cannot be SEEN. That does not entirely mean it can't be observed. There are other ways to observe things besides seeing them. In any case it can have an effect.

Pretty wordy question but I'll try to answer what I think was asked:

Is light invisible?

Yes and no for this question. They have something called a visible light spectrum which is the light we see. We are able to see this light because the wavelength it comes in is just the right thickness/height (extremely over-simplified). The light we cannot see includes things such as X-ray waves, infrared waves, and radio waves. All of these invisible light waves are invisible because the waves are either too small or too large for our eyes to register.

How do people tan?

Tanning essentially occurs when specific waves (not in the visible light spectrum) that hits the body. These waves are absorbed through the skin instead of viewed with our eyes (since they are not visible).

I believe this answers all your questions. Hope it helped!

All light is electromagnetic radiation. The spectrum consists of a range of different frequencies/wavelengths. Most frequencies are invisible to the human eye although around the middle of the spectrum, there is a small range of frequencies that can be identified by the eye.