Ultra Violet or UV rays are electromagnetic light radiation which has a wavelength shorter than that of visible light. However, UV's wavelength is longer than that of the X ray. The direct and the most common source of UV rays is the sun. The sun releases UV radiation.
The ozone layer, which is a part of our atmosphere, protects us from 99 per cent of the harmful UV rays as the ozone layer absorbs the UV rays from the sun even before it reaches the atmosphere on earth and harms us.
So we can say that the UV rays come from the sun, and when they pass the ozone layer, one per cent of UV rays reach the earth which is then called the UVA. UVA can pass through normal glass, where opaque objects prevent UVA from passing through them.
The ozone layer, which is a part of our atmosphere, protects us from 99 per cent of the harmful UV rays as the ozone layer absorbs the UV rays from the sun even before it reaches the atmosphere on earth and harms us.
So we can say that the UV rays come from the sun, and when they pass the ozone layer, one per cent of UV rays reach the earth which is then called the UVA. UVA can pass through normal glass, where opaque objects prevent UVA from passing through them.