It is defined by their wavelength. Different colors have different wavelengths. For example, radio waves have a really long wavelength, whereas gamma-rays have a very short wavelength.
Answer:
The curl is 
Explanation:
Given the vector function

We can calculate the curl using the definition

Thus for the exercise we will have

So we will get

Working with the partial derivatives we get the curl

Answer:
Germanium
Explanation:
Germanium is a chemical element that is grayish white metalliod