A laser used in a chemistry laboratory operates at a frequency of

PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation

Problem

A laser used in a chemistry laboratory operates at a frequency of 5.50×1014 s−15.50\times10^{14}\,\text{s}^{-1}. Useful constants: • c=3.00×108 m s−1c=3.00\times10^{8}\,\text{m}\,\text{s}^{-1} • h=6.626×10−34 J sh=6.626\times10^{-34}\,\text{J}\,\text{s} • NA=6.022×1023 mol−1N_{\mathrm{A}}=6.022\times10^{23}\,\text{mol}^{-1} (a) Calculate the wavelength of the laser light in nanometres. Report to an appropriate number of significant figures. (b) Determine the energy, in joules, of a single photon from the laser. (c) Calculate the energy, in kilojoules, delivered per mole of photons at this frequency. (d) Identify the perceived colour of the laser beam to the human eye, and explain how your calculated wavelength supports that identification.

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