You brandish the weapon used in the spell’s casting and make a melee weapon attack with it against one creature within 10 feet of you. On a hit, the target suffers the attack’s normal effects, and if the target is concentrating on a spell, the attack deals an additional 1d8 force damage.   The spell’s damage increases when you reach higher levels. At 5th level, the melee attack deals an extra 1d8 force damage to the target, and the damage the target takes if it is concentrating on a spell increases to 2d8. Both damage rolls increase by 1d8 at 11th level (2d8/3d8) and 17th level (3d8/4d8).