What type of electromagnetic wave is used in security pens?

The answer is; UV (ultraviolet)

The security pens use UV light to illuminate some marking on an object,such as a watermark, to identify its authenticity or owner. The markings are usually invisible to the naked eye under visible light. The marks are only visible when illuminated with UV light. This is because the marking is made of a fluorescent material that absorbs light of a  shorter wavelength (this case UV) and emits a longer wavelength (this case visible light).

water is a polar molecule. a chemical bond is a force of attraction between atoms or ions. bonds form when atoms share or transfer valence electrons. atoms form chemical bonds to achieve a full outer energy level, which is the most stable arrangement of electrons. so, false

explanation:

in h2o molecule, two water molecules are bonded by a hydrogen bond but the bond between two h - o bonds within a water molecule are covalent. the greater the electronegativity difference, the more ionic the bond is. bonds that are partly ionic are called polar covalent bonds. nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegativities of the two atoms are equal.