The speed of light \( c \) is related to frequency \( \nu \) and wavelength \( \lambda \) by the equation: \[ c = \nu \lambda \] where:
- \( c \) is the speed of light (approximately \( 3 \times 10^8 \, \text{m/s} \)),
- \( \nu \) is the frequency of the light wave,
- \( \lambda \) is the wavelength.
Thus, the correct answer is: \[ \boxed{(A) \, c = \nu \lambda} \]