A single wavelength of light that is unknown, together with blue light of one wavelength, is each directed normally at a diffraction grating. This gives two separate diffraction patterns, one corresponding to each wavelength. For the blue light, the third-order maximum is observed at the same angle as the second-order maximum for the unknown light. The wavelength of the blue light is $480\,\text{nm}$. What is the wavelength of the unknown light?
- A$320\,\text{nm}$
- B$720\,\text{nm}$
- C$960\,\text{nm}$
- D$1440\,\text{nm}$