Question

Which of the following cuts ultraviolet rays?
(A) Soda glass
(B) Crookes glass
(C) Pyrex
(D) None of these

Answer 1

Hint: (1) Glass is a non-crystalline amorphous solid and inorganic material which is generally hard, brittle and transparent in nature.
(2) Glass can be made up of thousands of different compositions. Depending upon the different chemical compositions, different glasses will have different electrical, thermal, optical and mechanical properties. One of the main constituents of many types of glasses is silica.

Complete step by step answer: Soda glass or soda-lime-silica glass is composed of about 70 percent silica or silicon dioxide, 15 percent soda or sodium oxide, 9 percent lime or calcium oxide and minor amounts of some other compounds. It is cheap, hard and can be resoftened a number of times. Due to these qualities, soda glass is used to make bottles, light bulbs etc. But it does not contain any component which is capable of absorbing UV rays. So option A is not correct.
Crookes glass is a kind of glass which contains mainly cerium oxide and silica. The cerium oxide can sharply absorb the harmful UV rays coming from the sun. So it is used in making sunglasses. So, option B is correct.
Pyrex glass is a kind of borosilicate glass that is composed of barium silicate and sodium silicate. It has very high chemical durability and hence it is used in making laboratory equipment. But none of its components have the ability to cut off UV rays. So, option C is incorrect.

Note: The main constituents of typical glass are categorized into formers, fluxes and stabilizers. The highest percentage of the mixture is made up of fomers. For example, in soda glass, the former is silica in the form of sand. The fluxes try to lower the melting temperature of the formers. For example, soda lowers the melting temperature of the silica. The stabilizers make the glass strong, tough and resistant to water. For example, in soda glass, lime is a stabilizer.