<span>Interference can only be explained if light is a wave. Youngs Double Slit experiment proved this, proving the wave nature of light.</span>
I think metal, steel and copper.
The U.S. Environmental Protection Agency (EPA) standard for nitrate in drinking water is 10 milligrams of nitrate (measured as nitrogen) per liter of drinking water (mg/L). * Drinking water with levels of nitrate at or below 10 mg/L is considered safe for everyone.
I think that mechanism is called a <em>"lens turret"</em>.
