Refraction causes light to bend as it passes from one material to another and the amount of bending depending on the refractive index of the material. In this activity we place a small beaker inside a larger beaker. We then fill the small beaker with vegetable oil, allowing the oil to overflow till the large beaker is filled as well. We find that the small beaker disappears when we do this! The glass of the beaker and the vegetable oil have refractive indices that are almost equal. Thus , as light passes from the small beaker to the oil outside, the light does not bend too much and we cannot see the small beaker.