Two layers in the separation funnel are the aqueous phase and the organic phase. For solvents lighter than water (i.e., density < 1), the organic phase will rest on top in the separatory funnel, whereas solvents denser than water (density > 1) will sink to the bottom.
Since, methylene chloride is denser than Brine therefore, methylene chloreide sinks at the bottom while methylene chloride stays on top.
Most of UV radiation is stopped by glass & this is why you will not get sunburns behind a glass. The glass simply filters out the UV radiation that is responsible for the sunburns & protect your skins from these energetic & somewhat harmful radiation
