An aquarium open at the top has 30-cm-deep water in it. You shine a laser pointer into the top opening so it is incident on the air-water interface at a 45angle relative to the vertical. You see a bright spot where the beam hits the bottom of the aquarium. The index of refraction of water is 1.33.

How much water (in terms of height) should you add to the tank so the bright spot on the bottom moves 5.0cm?

Express your answer to two significant figures and include the appropriate units.