Скачать или смотреть Invisible Glass | English

Place a small beaker in a big one and pour oil. On topping the big beaker with oil the small beaker will become invisible. Why? For doing this experiment you need a bottle of cooking oil, a mug of water and two good quality Pyrex beakers – small and big. First place the small beaker inside the big one. Fill the small beaker with water. The small beaker will be visible. Even on topping the big beaker with water you will be able to see the small beaker.
Then repeat the same experiment with cooking oil. Place the small beaker inside the big one. Fill the small beaker with cooking oil. You will be able to see the oil and the small beaker. Then fill the gap between the two beakers with oil. Slowly the lower portion of the small beaker will disappear. On filling the big beaker to the top with cooking oil the smaller beaker will become invisible.
As light passes from air to glass it slows down. Every material has a refractive index which is linked to the speed of light in that medium. The refractive index of Pyrex Glass and cooking oil is almost the same. So when light goes from glass to air to glass its speed does NOT CHANGE. As no reflection or refraction takes place hence the inner beaker becomes invisible.

This work is supported by IUCAA(www.iucaa.ernet.in) and TATA Trust (www.tata.com/aboutus/sub_index/Tata-trusts)

Credits:, Ashok Rupner, Manish Jain, Pradnya Pujari, Shivaji Mane, Jyoti Hiremath, Arvind Gupta, Vidula Mhaiskar TATA Trust: Education is one of the key focus areas for Tata Trusts, aiming towards enabling access of quality education to the underprivileged population in India. To facilitate quality in teaching and learning of Science education through workshops, capacity building and resource creation, Tata Trusts have been supporting Muktangan Vigyan Shodhika (MVS), IUCAA's Children’s Science Centre, since inception. To know more about other initiatives of Tata Trusts, please visit www.tatatrusts.org