Sources of UV

Question 1

What are some sources of UV? Which are used for phototherapy?

Answer 1

• Sun.
• Incandescent sources.
• Fluorescent lamps (low pressure Hg discharge with fluorescent coating) - These are the mainstay for phototherapy treatments.
• LEDs & lasers: Likely future development for phototherapy.

Question 2

What are the UVA, UVB and UVC regions?

Answer 2

• UVA: 400-315 nm.
• UVB: 280-315 nm.
• UVC: 280-100 nm.

Question 3

What kinds of UV from the sun are present on earth? What does this mean for humans?

Answer 3

• Large amount of UVA and small amount of UVB.
• Human body sensitive to UVB (hence reason for use in phototherapy) so protection is required.
• Eyes sensitive to UVA so protection is required.

Question 4

Provide some examples of UV uses.

Answer 4

• Room lighting bulbs have some UV component and LEDs have large blue light component.
• Curing.
• Germicidal irradiation with UVC.
• Woods lamp or black light (e.g. identification of some skin infections, banknote security etc.).

Question 5

What are two kinds of UV detector and what are their properties?

Answer 5

Vacuum thermopile:
- Converts optical energy to heat.
- Broad range of wavelengths.
- Flat response.
Photon detector:
- Photoelectric or solid state.
- Different diffusers/filters required.
- Restricted range of wavelengths.
- Detector must be matched to lamp type.
- Used in phototherapy QA.

Question 6

How is a detailed UV calibration performed?

Answer 6

UV spectrometry (e.g. with spectroradiometer).