A signal has a frequency of 800 kHz and travels at a speed of 3 x 108 m/s. Calculate its wavelength and period.

Rearrange the formula to solve for $\lambda$:

$$\lambda = \frac{v}{f}$$

Substitute the given values:

$$\lambda = \frac{3 \times 10^8 \text{ m/s}}{800 \times 10^3 \text{ Hz}}$$ $$\lambda = \frac{3 \times 10^8}{8 \times 10^5} \text{ m}$$ $$\lambda = \frac{3}{8} \times 10^{8-5} \text{ m}$$ $$\lambda = 0.375 \times 10^3 \text{ m}$$ $$\lambda = 375 \text{ m}$$

The wavelength of the signal is $\boxed{\text{375 m}}$.

Substitute the frequency in Hz:

$$T = \frac{1}{800 \times 10^3 \text{ Hz}}$$ $$T = \frac{1}{8 \times 10^5} \text{ s}$$ $$T = 0.125 \times 10^{-5} \text{ s}$$ $$T = 1.25 \times 10^{-6} \text{ s}$$

The period of the signal is $\boxed{1.25 \times 10^{-6} \text{ s}}$.