SCIENTIFIC FACTS

 

SCIENTIFIC FACTS

1.  Why does the same side of the moon faces the earth?

The moon rotates on its axis once 27 1/3 days, during which it revolves around the earth. Due to this fact, only one side of the moon will face the earth.

2.  Why does a needle sink in water whereas an iron ship floats?

The specific gravity of the needle which is a solid piece of iron is greater than that of water and so it sinks. But the ship is so designed that the weight of the ship is less than water displaced by it. The ship therefore floats while a needle sinks.

 3.  Why does the sky appear blue?

 The sky appears blue because of the scattering of light by dust particles or air molecules in the atmosphere. This scattering is inversely proportional to the fourth power of wavelength. 

As a result of this, the shorter wavelengths are profusely scattered. As a blue has the shortest wavelength of all colours, when we look at sky, it appears blue.

 4.  Why the rainbow seen after the rain?

 The rainbow is formed only by the reflection of the sunlight at the back of the rain drops which acts as prisms and which are quivering in the atmosphere immediately after the rain stops. 

So the dispersed rays of sunlight having suffered deviation give rise to concentrated beam of light indicating all the colours of the light.

 5.  What causes wrinkles in the skin?

 Wrinkles are caused mainly by ultraviolet rays’ radiation from the Sun. Over the years the ultraviolet rays break down the middle layer of skin, the dermis, come it to loosen and allowing wrinkles to form. With extreme age, the dermis worsens on its own accord. To decrease the wrinkles in the skin, one should limit exposures to direct sunlight, such as by using sun creams. Wrinkles are more likely to occur among people with lighter skin.

6.  How are the green plants active in modifying the composition of air?

    In the presence of sunlight during the process of photosynthesis, they liberate oxygen equal to the amount of the carbon dioxide taken in. This balances the proportion of oxygen and carbon-dioxide in the air. Thus this process helps in modifying the composition of air to a great extent.

7.  How does a parachute enable a person to descend safely from an aircraft?

 The gravitational force of the earth attracts the man towards it. But the parachute is subjected to considerable resistance by the air and thus slows down the speed of descending man.

8.  How do bubbles get into fizzy drinks?

When a fizzy drink is opened bubbles form inside the drink. These are bubbles of a gas called carbon-dioxide that help the drink taste sharp. The gas is dissolved in the drink when it is made at the factory, where the carbon dioxide gas is forced into the drink under pressure so that it dissolves in the liquid.

The drink remains under pressure in the bottle or so that the gas stays dissolved in the drink. However, when the bottle or can is opened, the pressure is released. This is why the drink tries to get out as it is opened. The carbon dioxide escapes and form bubbles.

9.  How the distance between stars is measured in light years and how long is a light year?

According to the scientists, the stars are spaced so far apart that any measurement of the distance between them in familiar units would be unwieldy. So scientists created a more manageable astronomical unit called the “light year”, which is the distance light takes to travel in one year, at a speed of about 186,200 miles a second. One light year is about 6,000,000,000,000 miles.

10.Why does hard water not readily form lather with soap?

 Soap is odium salt of an organic acid. When soap is mixed with water they react chemically to form sodium hydroxide and organic acid is eliminated. The sodium hydroxide thus produces causes the lather. 

When soap solution is added to hard water, the soap reacts with the salt such as chlorides and bicarbonates present in hard water. Only after these salts are removed as organic salts, soap reacts with water gives sodium hydroxide which causes the lather.