For which optical devices does d sometimes have a positive value?

an ion is a charged atom or molecule. it is charged because the number of electrons do not equal the number of protons in the atom or molecule. an atom can acquire a positive charge or a negative charge depending on whether the number of electrons in an atom is greater or less then the number of protons in the atom.

1 - wave length

2 - amplitude

3 - crest

4 - trough

explanation:

duh.

where’s the list ? the question is incomplete