A wave carries energy from one place to another. Some waves need a(n) medium to carry the waves. For example, water waves travel through water. Light waves are different because they can travel through empty space, which contains no liquid, gas, or solid. Light waves bend as they go from one substance to another. This property is called refraction. Some telescopes and eyeglasses use this characteristic of light. Another property of light is reflection, or the bouncing of waves off a surface. Reflection of light is the basis of mirrors and some telescopes.