Explanation: In this video, it demonstrates a light trick, about how an object can “Vanish” in the oil. Which used a beaker filled with oil, then simply put in the other smaller beakers, also several stirring rods. At first, when he put the stirring rod into the water, we can clearly see that, but when he put the same stirring rod into the oil, the part of stirring rod in the oil “disappeared”. Then, he showed us, when he put the smaller beaker into the oil, same thing happened, we can barely see the beaker in the water. That’s becuase the index of refraction of oil and stirring rod and other beakers are very similar. Refraction occurs when a wave changes in the direction as it pass from one medium to another. The index of refraction describes how much the light will bend numerically, this number indicated the speed of light in the certain medium. When light passes from air into glass, it slows down. It changed the speed leads to the light reflect and refract. When the difference between the index of refraction of two different materials decreases, the less reflection and refraction while the light travel through two mediums. Therefore, it makes the transparent object looks like “invisible” in that medium.