To overcome an energy barrier between reactants and products in a chemical reaction, energy must be provided to get the reaction started. this energy, which is recovered as the reaction proceeds, is called:

1b. convection2f. the same

The main types of electromagnetic radiation. radio  waves have  the lowest frequencies  and  longest  wavelengths, while gamma  waves have highest frequencies  and shortest wavelengths. the wavelengths vary across the electromagnetic spectrum from about 10–15 m to more than 104 m.hope it !