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

Answer 1

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