Why photochromic glasses turn dark when exposed to sunlight?

Why photochromic glasses turn dark when exposed to sunlight

The lenses of photochromic lenses are made of glass that is mixed with minute crystals of light-sensitive silver iodide or bromide. The crystals are so tiny that they have a length of only 50 angstroms, and to make its length clearer, a single angstrom is equivalent to 0.0000000001 meters. As these crystals … Read more

What’s the reason for keeping a hole in the center of a parachute?

What's the reason for keeping a hole in the center of a parachute?

What could possibly happen if there was no hole in the middle of the parachute to let some of the air escape? The problems for hole-less parachutes were prominent during the First World War when paratroopers would use parachutes without holes and consequently faced two serious risks. The first risk arose when … Read more

How is ‘expiry date’ of medicines determined?

How is 'expiry date' of medicines determined?

Some decades ago there were no chemists’ shops. Instead of chemists druggists used to mix various compounds according to physicians’ prescriptions and sell them either in powder form or liquid form. Sometimes physician’s assistant used to prepare such mixture in the dispensary itself so he was known as compounder. These types of medicines … Read more

What technique is used in microwave ovens to cook food in minutes?

What technique is used in microwave ovens to cook food in minutes

Microwave ovens have provided the mankind with the whole new way of cooking, quite unlike the conventional method followed since thousands of years. When cooking is done in a customary manner, the heat that comes from a conventional gas stove is transferred to food by conduction. The heat is passed first to … Read more

Why is water used as a fire extinguisher?

Why is water used as a fire extinguisher

One might wonder, if hydrogen is a highly combustible gas, while oxygen helps it in combustion, then why does the combination of both of these elements as H2O or water have the ability to extinguish a fire? The answer lies in the difference between mixture and compound found in H2O. At the … Read more

What is the process of turning Mercury into Gold?

What is the process of turning Mercury into Gold

For centuries, people have tried to find a method to produce gold, one of the most valuable materials in the world. Gold has been the primary method of currency for centuries, perhaps even millennia. Once, it backed United States currency, though those does are behind the country. Gold is universally valuable for … Read more