for instance, how come we’re told to wear sunscreen in broad natural day-light but not artificial light like indoors?
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We use sunscreen to protect ourselves from ultraviolet light, a wavelength that is just beyond the visible part of the spectrum. The sun produces much more ultraviolet light than a lightbulb does. Ultraviolet light has a shorter wavelength and therefore more energy than visible light; it is therefore able to cause the kind of damage to our skin that causes sunburn and, potentially, skin cancer.
Light is only a single type electromagnetic radiation. Specifically, what we call light refers to **visible** light.
There are many other types of electromagnetic radiation and they lie outside the visible light part of the electromagnetic spectrum. X-rays, gamma rays, radio waves, and so on.
A light bulb only emits radiation in the visible part of the spectrum (and a little bit of infrared, since most lights emit heat as well).
The Sun is a giant ball of gas that functions as a fusion reactor. The radiation it emits goes far beyond visible light. It emits ultraviolet, infrared, radio waves, X-rays and gamma rays.
Out of those, the radiation with longer wavelengths than visible light (infrared, radio, microwaves) are not generally harmful to us since they carry less energy.
The radiation with shorter wavelengths (ultraviolet, X-rays, gamma rays) is **dangerous**. The damage can range from a simple sunburn, to skin cancer.
Thankfully, the earth’s atmosphere filters out most of the nasty stuff. What you’re usually left with is ultraviolet. That’s what you use sunscreen for.
In short, you don’t have to worry about none of the harmful radiation that the Sun emits from a regular light bulb.
A (classical) house light is a simple tungsten filament heated until it becomes incandescent. Think of how metal glows when it’s red hot. At that temperature, it radiates light that falls within the visible spectrum, which is why you can see it.
On the other hand, the Sun being a fusion reactor, is millions of degrees hotter. At those temperatures, the naturally radiated energy falls in the higher, more dangerous electromagnetic bands such as X-rays and gamma rays.
Some lights are red, some are blue, some are green. Take a look at any gaming PC and youll probably see all 3. How much energy is in the individual waves of light (photons) determines what color it is. Red is low energy, blue is high energy, violet is even higher energy. The lights we use in our houses are whitish, which means they have some of all these colors. The sun also makes all these colors, but it also makes light that we cant even see. Our eyes can only see certain kinds of light that is medium energy light, the stuff most common around us. But the sun is much more powerful than a lightbulb and makes light with a ton more energy. These high energy light waves are called ultraviolet or UV. We cant see them, but since they have so much more energy than visible light it can actually damage our skin
TLDR: the sun is a lot more powerful and the light it makes has more energy!
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