The rays of the Sun that cause tanning and burning are in the ultraviolet portio

Question

The rays of the Sun that cause tanning and burning are in the ultraviolet portion of the electromagnetic spectrum. These rays are categorized by wavelength: So-called UV-A radiation has wavelengths in the range of 320-380 nm, whereas UV-B radiation has wavelengths in the range of 290-320 nm. Calculate the frequency of light that has a wavelength of 345 nm . Calculate the energy of a mole of 345 nm photons. Which are more energetic, photons of UV-A radiation or photons of UV-B radiation? Which are more energetic, photons of UV-A radiation or photons of UV-B radiation? photons of UV-A radiation -photons of UV-B radiation

Explanation / Answer

a) wavelength = 345 nm = 345 x 10^-9 m

frequency = C / wave length

                 = ( 3 x 10^8) / (345 x 10^-9)

               = 8.70 x 10^14 Hz

b)

energy = h x frequency

             = (6.625 x 10^-34) x (8.70 x 10^14)

            = 5.76 x 10^-19 J

c)

UV-B radiation is more energetic

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