The law of conservation of mass states that in a chemical reaction, mass is neither created nor destroyed. that means, the total
mass for the reactants needed to equal the total mass of the products. the reactants for photosynthesis are 6 carbon dioxide, 6 water and sunlight. the mass of these reactants adds to equal the mass of the products, which are 1 glucose and 6 oxygen. there are equal amounts of each atom on both sides of the chemical equation. the law of conservation of energy states that energy cannot be created nor destroyed. this is a little more confusing because energy (sunlight) is a reactant in the equation and not a product, so it had to go somewhere. energy can be converted from one form to another. in the case of photosynthesis, energy is converted from sunlight into glucose. glucose is a carbohydrate which is a molecule that the body can break down for energy.
Well all reactions need energy to start it. The light is the energy that the reaction requires to start it. Sunlight also has no mass in the first place so laws of conservation of mass don't apply to it.
