UVA and UVB Rays
There are 3 types of Ultra Violet (UV) rays from the sun: UVA, UVB and UVC. UVC does not reach the earth's surface. So we won't be talking about UVC in this post.
The light we see is the visible rays from the sun. We cannot see UV rays.
The heat you feel is from the infrared rays of the sun. We cannot feel the UV rays (until after it causes the damage).
- Only 10% of UVB reaches the earth's surface.
- UVB is responsible for sunburn.
- UVB is usually high around midday. It is higher in summer than in other seasons.
- UVB causes skin cancer.
- UVB is blocked by glass. If you are indoors, nearly all UVB will be absorbed by the glass (have you ever got sunburn when you are indoors?).
- UVB is required for the production of Vitamin D in our bodies.
- 90%+ of UVA reaches the earth's surface.
- We did not realise the dangers of UVA up until recently.
- UVA penetrates the skin and reaches the inner layers of skin.
- It damages skin cells.
- It damages collagen and elastin in-between the cells.
- Causes wrinkles and sagging of the skin.
- UVA is responsible for the premature ageing of the skin.
- UVA causes skin cancer.
- UVA is not specific to certain times of the day and seasons. It is present 365 days and in all seasons.
- UVA can penetrate glass. So if you are indoors, UVA can reach you! UVA is why we need to wear sunscreen even if we are indoors.
UV Index measures the intensity of both UVA and UVB radiation from the sun. Higher the number, the higher the strength of the radiation reaching us.