What term and what definition..
Answer :- In a light wave the property of wave which tells about the color of light is it's Wavelength .
Wavelength is the distance between one crest and one through , also it is the distance after which the wave repeat itself !
It's SI unit is meter !
It is scalar quantity !!
Different Wavelength of light have different color !!
• VIBGYOR
i.e, Violent , Indigo , Blue , Green , Yellow Orange, and Red along with their shades are the colors which we can see !!
• They almost range from 400nm to 700nm ( visible range of light )
Reaction 3 is the double displacement reaction.
Double displacement reaction occurs when the negatively and the positively charged ions of the compounds interchange their position when the new compound in the product is formed.
<h3>Which is a double displacement reaction?</h3>
In the <u>first reaction</u>, the element lead (Pb) is not an ion and no exchange of the cations or the anions occurs hence it is not a double displacement reaction.
In the <u>second reaction</u>, one compound is getting split into two new compounds and is a decomposition reaction.
In the <u>third reaction</u>,
in
and
in
are anions and cations and exchanges their places to produce two new compounds 
In the <u>fourth reaction</u>, a single compound is generated as the result of the combination reaction and hence, it is not the double displacement reaction.
Therefore,
is the double displacement reaction.
Learn more about double displacement reaction here:
brainly.com/question/10091171
<span>An aqueous solution is produced when a solute dissolves in water. The biggest responsible is the water that is the solvent of substances in smaller proportion as some ions of K +, Na +, Cl -, forming true solutions. Occurs when a solute dissolves in the water solvent, the separation between the substances is atomic, molecular or ionic, depending on the solution.</span>