UV-Vis Spectroscopy (or Spectrophotometry) is a quantitative technique used to measure how much a chemical substance absorbs light. This is done by measuring the intensity of light that passes through a sample with respect to the intensity of light through a reference sample or blank.

UV-Vis is often called a general technique, as most molecules absorb light in the UV-visible wavelength range. The UV range extends from 100–400 nm, and the visible spectrum ranges from 400–700 nm. The monochromator can be scanned over a wavelength range to provide an entire absorbance spectrum.

The Principle of UV-Visible Spectroscopy is based on the absorption of ultraviolet light or visible light by chemical compounds, which results in the production of distinct spectra. Spectroscopy is based on the interaction between light and matter.

UV Index 8-10 means high risk of harm from unprotected sun exposure. UV Index of 11+ means a very high risk of harm from unprotected sun exposure.

A computer model uses the ozone forecast and the incident angle of sunlight at each point to calculate the strength of UV radiation at ground level. Sunlight angle is determined by latitude, day of year, and time of day (solar noon).

New Zealand

Time of day: UV rays are strongest in the middle of the day, between 10 am and 4 pm. Season of the year: UV rays are stronger during spring and summer months. This is less of a factor near the equator. Distance from the equator (latitude): UV exposure goes down as you get further from the equator.

UV radiation levels and therefore the values of the index vary throughout the day. In reporting the UVI, most emphasis is placed on the maximum UV radiation level on a given day.

A UV Index reading of 11 or more means extreme risk of harm from unprotected sun exposure. Take all precautions because unprotected skin and eyes can burn in minutes. If outdoors, seek shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses.

Blazing world record: Strongest UV rays ever measured on Earth. A “perfect storm” of ozone-destroying chemicals sent cancer-causing UV-B radiation soaring at the top of a South American volcano in 2003, a new study reports. On Dec. 29, 2003, a world-record UV index of 43.3 was detected at Bolivia’s Licancabur volcano.

Whether the UV Index is 1 or 5, you should always wear a broad spectrum sunscreen of at least SPF 30. When the UV Index number is high (aka above 6), it would be best to layer your sunscreen––but again, we’re big fans of doing this on a daily basis, regardless of what the UV Index is.

Good UV Index for tanning

1. UV Index 0 – 2. Low exposure level. Average time it takes to burn: 60 minutes.
2. UV Index 3 – 5. Moderate exposure level. Average time it takes to burn: 45 minutes.
3. UV Index 6 – 7. High exposure level.
4. UV Index 8 – 10. Very high exposure level.
5. 11+ UV Index. Extreme exposure level.

While many believe tanning in the evening does not reap the same results, others prefer it. But is it really possible to tan in the evening? If you want a short answer, then yes, it is completely possible to get a beautiful tan even if you spend time in the sun after 5 PM.

Take these steps to stay sun-safe: Seek shade: Limit your direct exposure to the sun, especially between 10 a.m. and 4 p.m., when UV rays are strongest. Cover up: When you are out, wear clothing and a wide-brimmed hat to protect as much skin as possible.

The FDA recommends choosing a sunscreen that provides:

• A sun protection factor (SPF) of at least 15 or higher. The SPF rating on sunscreen refers to how long it can protect a person from sunburn before it needs to be reapplied.
• Broad spectrum coverage.
• Water-resistant protection.

Sunburns not only leave us with uncomfortable skin during the day, but also at night. Skin damaged by the sun can sabotage sleep – sometimes for a few nights at a time – but thankfully, there are some tried and true ways to find a little relief.