The wavelength of red light is about 700 nm: λred = 700 nm. Which is larger, a grain of sand (diameter roughly 0.2 mm) or a wave of red light? How many times larger?

The grain of sand is larger by a factor of about 286.

Explanation:

We express both values in standard form in the SI unit of metre so that the comparison can be easily done:

Diameter of grain of sand =

It is seen that the grain of sand is larger.

The ratio of the sizes is given by

the right answer is 0.3 meters per second