Question

4 of 5 Constants There are two categories of ultraviolet light. Ultraviolet A (UVA) has a wavelength ranging from 320 nm to 400 nm. It is necessary for the production of vitamin D. UVB, with a wavelength in vacuum between 280 nm and 320 nm, is more dangerous because it is much more likely to cause skin cancer. Find the frequency ranges of UVA.

Answer 1

Answer: UVA rays occupy the frequency range between 7.1 . 10¹⁴ and 9.4. 10¹⁴ Hz.

Explanation:

UV rays are simply electromagnetic waves, which wavelength is just below the visible spectrum (hance the name ultraviolet, meaning beyond violet).

As any elecromagnetic wave, propagates in the free space at the same speed that light does, i.e. 3.10⁸ m/s.

Also, we know that there exists a direct relationship between the wave speed, her wavelength (distance travelled by the wave during one cycle time) and the frequency (the inverse of the time needed to complete one cycle).

This relationship can be written as the following equation:

v = λ . f   ⇒  f = v/λ

Replacing by the extreme wavelengths, we find the corrresponding limit frequencies as follows:

f₁ = 3.10⁸ m/s / 320 . 10⁻⁹ m  ⇒ f₁ = 9.4 . 10¹⁴ Hz.

f₂ = 3.10⁸ m/s / 400 . 10⁻⁹ m ⇒ f₂ = 7.1 . 10¹⁴ Hz.

Answer 2

Answer:

The answer is: The wavelength is approximately between 10 nm (10 x 10-9 m) and 400 nm (400 x 10-9 m).

Explanation:

Ultraviolet radiation or UV radiation is called electromagnetic radiation whose wavelength is approximately between 10 nm (10 x 10-9 m) and 400 nm (400 x 10-9 m). Its name comes from the fact that its range starts from shorter wavelengths than what we humans identify as the violet color, but that light or wavelength is invisible to the human eye by being above the visible spectrum.

Name -  Abbreviation - Wavelength (nm) - Energy per photon (eV)

Ultraviolet A (long wave) -UVA- 400 - 315          3.10 - 3.94

Ultraviolet B (medium) -UVB-     315 - 280          3.94 - 4.43

UV C (shortwave) -UVC-            280 - 100           4.43 - 12.40

Near ultraviolet (near) -NUV-    400 - 300           3.10 - 4.13

Middle ultraviolet (middle) -MUV- 300 - 200      4.13 - 6.20

Far ultraviolet (far) -FUV-           200 - 122            6.20 - 10.16

Lyman-alpha -H line Lyman-α / Ly-α- 122 - 121    10,16 - 10,25

Vacuum ultraviolet -VUV-          200 - 10              6.20 - 124

UV ultraviolet -EU-                      121 - 10               10.25 - 124

The types of UV radiation (A B and C) are related to the damage they cause in humans: UV-C radiation is the most harmful to life.

The answer is: The wavelength is approximately between 10 nm (10 x 10-9 m) and 400 nm (400 x 10-9 m).