An electromagnetic wave is directed normally onto a diffraction grating. A second-order maximum appears at an angle of $30^{\circ}$ to a normal to the grating. The grating contains $5000$ lines per $\text{cm}$. What is the wavelength of the wave?
- A$2.5 \times 10^{-7}\,\text{m}$
- B$5.0 \times 10^{-7}\,\text{m}$
- C$1.0 \times 10^{-6}\,\text{m}$
- D$5.0 \times 10^{-5}\,\text{m}$