What is a Bolometer?

            Bolometer is an instrument that is used to measure radiation temperature. It is a kind of Resistance Bridge. Its one arm consists of a blackened metal strip. When the radiations fall on the metal strip the temperature rises. This increase in temperature measured by a bolometer. This is a very sensitive instrument.

Bolometer

            A U.S. scientist, Samuel P. Langely invented this instrument in 1880. In this first bolometer, a Wheatstone bridge was used along with a galvanometer that produced a deflection proportional to the intensity of the radiation. Since then several other thermal devices have been developed but bolometer remains one of the most effective and convenient infrared detectors. It is because it does not need cooling and can be operated with great ease.

            Now the question arises, what is the principle of working of this instrument? The principle on the basis of which a bolometer operates is that a temperature changes is produced by the absorption of radiation this causes a change in electrical resistance of the material used in the fabrication of the bolometer. This change in resistance can be used to sense radiation.

            There are several types of bolometer in use today. One type has two strips bridge the circuit, their electrical resistance changes. The change of resistance can be used to measure the temperature. This instrument is so sensitive that it can detect changes in temperature as small as 0.001 degree centigrade.

            Another type of bolometer known as spectrum bolometer consists of a single strip of metal. It is used for examining the distribution of intensity of radiation in a spectrum.

How does a Microwave Oven Work?

            Microwave oven takes less than one-tenth of the time taken by other methods of cooking. It has made life much easier for many people. The application of modern technology in domestic appliances has made our lives more comfortable. Washing machines, vacuum cleaners, microwaves ovens, telephones, computers, etc. area few examples that meet the demands of a modern society. How does a microwave oven work?

Microwave Ovens are used for Rapid Cooking at the Appropriate Temperature

            A microwave oven does not have burning flames or red-hot plates like a gas and electric cooker. Its operational mechanism is simple. The food is put into the microwave oven and a switch is pressed. Inside the oven, invisible energy rays bombard the food, and it gets cooked.

Microwave Oven Waves 

            The oven gets its name from the rays that cook the food-the rays are called microwaves. Microwaves are a part of the spectrum of electromagnetic waves, which includes light waves and x-rays. They have wavelengths from about 30 centimeters to a millimeter, which places them between the shortest radio wave and infrared wave. One of the major properties is that it excites the molecules, especially in liquids, which makes them vibrate and get heated up. It is for this reason that food with large water content gets cooked very quickly.

            The source of microwaves in the oven is a magnetron. It is a two electrode valve for generating high frequency oscillations. Microwaves generated by the magnetron travel down a metal duct and are scattered around by a metal fan for even cooking. The molecules strike against each other and the friction produces heat. Water content in the food gets heated up rapidly and the food gets cooked.

            Microwave ovens are potentially a dangerous source of radiation. It is for this reason that microwave ovens are lined with metal and have strong doors. The oven does not function unless the door is closed properly, thus ensuring safety. Most modern ovens contain small computers that automatically cook the food. Microwave ovens are most preferred and widely used in restaurants, hotels and homes.