The speed of light is commonly denoted by the lowercase letter c in equations.
For example:
- In Einstein’s famous equation: E = mc²,
the c represents the speed of light in a vacuum. - In physics formulas related to light and electromagnetic waves, c always stands for the constant speed of light, approximately 299,792,458 meters per second.
So, whenever you see c in scientific or mathematical contexts, it almost always refers to the speed of light in vacuum.