UVA rays:
... meet the earth’s surface as part of the sun’s rays. They cause various photo-chemical processes and have a noticeable pigmentation, practical but not erythemal (inflaming) effect. UVA rays like light can penetrate glass and transparent synthetics.

UVB rays:
... have a pigmenting and strong inflaming effect. They cause the formation of pre-vitamin D. The radiation is used for therapeutic purposes (anti rachitic). At sea level their percentage amount is lower than it is in the mountains. These waves cannot penetrate normal window glass as it is with short UV waves.