Question

A special type of glass which contains cerium oxide and does not allow the passage of ultraviolet. This glass is used for making lenses. The glass is called:
A) Flint glass
B) Crookes glass
C) Hard glass
D) Pyrex glass

Answer 1

Crooke’s glass mainly contains silica and cerium oxide. The Crookes glass was invented by Sir William Crookes, it can absorb most of the ultraviolet rays coming from sunlight. You have to look out for the correct formula of cerium oxide used in Crookes glass.

Complete answer:
This glass mainly contains cerium oxide which absorbs the ultraviolet rays, and thus it is used to make lenses for eyeglasses.
Apart from cerium oxide, Crooke’s glass also contains silica. This glass is specially made to stop ultraviolet rays that come from sunlight.
Sir William Crookes invented the Crookes glass, he was an English chemist and physicist. The name Crooke’s glass is named after Sir William Crookes.
The Crookes glass can absorb $100\%$ of ultraviolet rays coming from sunlight. This makes Crooke’s glass perfect for the usage in lenses of eyeglasses.
The formula of cerium oxide is $Ce{{O}_{2}}$ . Cerium oxide also has another compound with the formula as $C{{e}_{2}}{{O}_{3}}$ , but this compound is unstable and undergoes oxidation to form $Ce{{O}_{2}}$ .
As the name suggests for flint glass, it is used to make glasses that flint. They are also used to make prisms.
Hard glass is also called Borosilicate glass as it mainly contains silica and boron oxide.
Pyrex glass is a type of glass which is resistant to heat, chemicals and electricity, and thus they are mainly used to make chemical apparatus and industrial equipment.
And hence the correct answer is option B.

Note:
The cerium oxide used in Crooke’s glass is $Ce{{O}_{2}}$ and not the $C{{e}_{2}}{{O}_{3}}$ . As $C{{e}_{2}}{{O}_{3}}$ is unstable, it undergoes oxidation to form $Ce{{O}_{2}}$ . Thus, it is important not to mistaken $Ce{{O}_{2}}$ for $C{{e}_{2}}{{O}_{3}}$ in the formation of Crooke’s glass.