My Science School

The colour of an object is determined by the  spectral composition of the light reflected by it.

When a surface is dry, the reflected light rays corresponding to the colour of the surface

are superposed with diffused white light arising out of random scattering resulting from

the roughness and irregularities of the surface. In the case of clothes, this superposition tends to fade the reelected colour. 

If clothes are immersed in water, all the kinks and interspaces are filled with

water. This minimises scattering of light on the surface. So the reflected light

comes out unsuppressed with the basic hue of the cloth. Hence it looks richer

and darker than when dry.

 

Continue reading "Why do clothes look dark when immersed in water?"

TFM is the abbreviated form of ‘Total Fat Matter’ in a soap. According to the

provisions of the Drugs and Cosmetic Rules, in all  toilet soaps, the TFM content 

has to be mentioned in terms of percentage on the wrapper of the product apart from the other details required under the rules. 

The standard fixed by the Bureau of Indian Standard (formerly I.S.I.), the ideal and safe percentage of TFM in any toiletary  preparation should be between 60 and 80 per cent. 

However, having been unsure of the standard, even many, of the reputed soap  manufacturers have omitted ‘toilet soap’ from their name and simply state ‘bathing bar’. Similarly shaving soaps are marketed as showing  creams without mention of TFM content.

Water boils at 100° C at sea level. The atmospheric pressure which acts on water is 14.7 psia (pounds per square inch - absolute). This atmospheric pressure varies with the altitude. So the boiling point of water is influenced with respect to the atmospheric pressure. Perfect vacuum is 'O' psia. Any pressure between 14.7 psia and o-psia is 'negtive pressure', that is, partial vacuum. Vacuum drying takes advantage of the decrease in the boiling point of water that occurs as the pressure is lowered. This type of drying keeps the products with very low moisture content. If salt water is subjected to this negative pressure, the water will boil by taking the heat from the  ambient. In case of reducing atmospheric pressure, i.e. 14.7 psia to 0.15 psia, water will start boiling at 7°C itself.

Freeze drying, convection  drying, microwave drying, dielectric drying, conduction drying, U-V radiation drying, etc, are some other drying methods applied in various  industries such as textile, plywood manufacturing, paper products, production of dried milk, soaps, detergents, pharmaceuticals, serums,  bacterial and viral cultures, vaccines, fruit juices, vegetables, coffee and tea extracts, sea foods, meats, cereals etc.

Answer 1- Food poisoning is caused either by ingestion of food contaminated with chemical ormetallic poisons, bacteria orbacterial toxins or by eating poisonous foods such as certain species of mushrooms.Molds and bacteria are responsible for microbial food poisoning. Molds grow on food (especially if they are moist). During their growing period they produce toxic substances called mycotoxins whose effect on man and animals cause mycotoxicosis. Mycatoxins remain the the food long after the mold producing them has died and can therefore be present in foods that are not visibly moldy. Some mycotoxins are stable and survive the usual conditions of cooking and processing.

 Food grains, especially bajra, rye and jowar get infected with a parasitic ergot fungus Claviceps purpurea. Ergotism, a toxicosis results from eating grains contaminated with this fungus. Alimentary toxic aleukia (ATA) is another mycotoxicosis caused due to eating moldy grains

 

Continue reading "What is food poisoning?"

Earth rotates from west to east causing the Sun, the Moon, stars andother planets rise from

east and set in the west. On the surface of the eartheach point is moving eastward with

respect to an astronaut in space.

Thus if a rocket is launched at a small angle eastward vertically the speed of earth gets added to

the rocket's speed. This reduces the amount of fuelrequired. If the rocket is inclined along any

other direction, the speed of the earth gets subtracted from the speed of rocket and will

necessitate burning of more fuel.

In addition, in case of any failure during launch the rocket will fall back to the earth.

Hence if it is launched from the east coast, the rocket will fall into the sea only. If it is launched from the west coast, in case of failure, the rocket will fall on the land endangering human habitats. Thus choosing eastward inclination is scientific but choice of eastern coast concerns safety.

In normal telephone exchange systems, a pair of wires extends each telephone instrument to the telephone exchange.

Normally, copper conductors are used to give loop to indicate the exchange that the 

Continue reading "How does a cell phone work?"