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Sharpen Your General Knowledge
Shamim Ansary:
Did Dinosaurs and Humans Ever Coexist On Earth?
Dinosaurs and humans did not coexist on earth.
Dinosaurs first appeared in the Triassic period, about 220 million years ago, and disappeared at the end of the Cretaceous period, about 65 million years ago.
Modern humans (Homo sapiens) appeared only about 25,000 years ago.
Movies that show humans and dinosaurs existing together arc only Hollywood fantasies.
Shamim Ansary:
What Is Radiation, Which Objects Emit Radiation, and How Is the Wavelength of Radiation Measured?
Radiation is energy emitted by a source such as a planet, star, or your own body.
We measure radiation in wavelengths. Radiation travels in rising and falling motions called waves, like waves in the ocean.
Wavelengths are measured from the tip of one wave to the tip of the next.
Our eyes can register light waves, which are relatively short, but wavelengths of other kinds of radiation are too short or too long for us to be able to see them.
Radiation waves can also be measured by frequency, or how many waves pass a point within a certain amount of time.
Imagine you are standing in the ocean with a stopwatch.
You time the waves, counting how many pass you within one minute. If three waves go by, the wave frequency is 3 cycles per minute.
Radiation is usually counted in cycles per second (cps): 1 kilohertz (kHz) = 1,000 cps, and 1 megahertz (mHz) = 1 million cps.
Shamim Ansary:
Why Do Trees and Leaves Change Color In Autumn and What Causes the Color Change In Fall?
The leaf color changes of autumn result from a complex interplay of factors of temperature, sunlight and moisture, all dependent on timing.
Not all the processes are predictable, but it is known that sunny days and cool nights in late summer and early autumn make for a particularly bright display of reds.
The yellow display operates separately from the red display, though both result from a shutdown of photosynthesis.
Shorter days signal the development of a layer of cells at the base of the leaf, called the abscission layer, that cuts off the water supply and later severs the leaf.
This stops production of chlorophyll, the green chemical at work in photosynthesis.
The chlorophyll breaks down, unmasking pigments already present in a leaf that will “turn†yellow: the xanthophylls, or yellows, and carotenes, the same orangey-yellow chemicals found in vegetables like carrots.
Still another class of pigment, the anthocyanins, is manufactured more quickly as summer ends.
As the leaf is cut off from its circulation, its sugar is trapped in the leaf and turns into anthocyanins, which depending on the species can be red, purple or maroon.
Cool nights in autumn inhibit the loss of sugar from the leaves, but brilliant sunshine promotes the maximum sugar synthesis and its transformation into anthocyanins.
A mild to moderate drought also stimulates anthocyanin production.
Drought or stresses like insects early in the season have comparatively little effect on the eventual nature of the color display, but can cause premature browning and leaf loss.
Shamim Ansary:
Why Does Black Tea Lighten or Change Color When You Add Lemon Juice and What Causes the Chemical Change?
The simple answer to why black tea changes color is that adding lemon juice alters the acidity of the tea and the color change is an indication of this.
The color change is the same way that litmus paper changes color.
A similar effect can be observed by substituting the tea with some cooked red cabbage juice.
Tea leaves are rich in a group of chemicals known as polyphenols that amazingly account for almost one-third of the weight of the dried leaf.
Both the color of the tea and much of its taste are due to these compounds.
One group of polyphenols, the thearubigins, are the red-brown pigments found in black tea and constitute between 7 percent and 20 percent of the weight of dried black tea.
The color of black tea is also influenced by the concentration of hydrogen ions in the water.
Thearubigins in tea are weakly ionizing acids and the anions, or negatively charged ions, they produce are highly colored. If the water used to brew tea is alkaline, the color of the tea will be deeper due to greater ionization of the thearubigins.
If lemon juice, which is an acid, is added to the tea, the hydrogen ions suppress the ionization of thearubigins, and that makes the tea lighter.
Interestingly, the theaflavins, the yellow-colored poly-phenols in black tea, are not involved in the change in color that is associated with a change in acidity.
Shamim Ansary:
Why Are Bread, Potatoes, Rice, Sugar, and Diamonds Not Black In Color If They’re Made of Carbon?
The best way to explain is with an example.
Sodium reacts violently on contact with water, while chlorine is a highly toxic greenish-yellow gas.
However, sodium chloride, the compound which contains these two elements, is harmless common salt, showing the properties of an element are very different from the properties of that element’s compounds.
The black powder used to produce a photocopy is finely ground carbon in its elemental form.
The particles are extremely small and arranged at random. Any light which falls on them is absorbed and not re-emitted, so the powder looks black. The sandwich certainly contains carbon but not in its elemental form.
Here, it is combined with oxygen and hydrogen as carbohydrates.
These compounds have their own properties which are nothing like the properties of their constituent elements. The slices of bread emit light of many wavelengths reasonably well, so when we look at bread in daylight, it appears white.
Carbon is normally found as an amorphous solid, which means it lacks a definite crystalline structure. Because of this, and because of the position of certain electrons in the outer orbits of the carbon atom, light is absorbed and not re-emitted.
This means the carbon atoms in graphite, soot and carbon black appear black.
Diamond, which is also carbon, is normally clear, because its crystalline structure alters the electrons and their positions to create a colorless crystal. Diamonds can be colored if other atoms, usually metals, are present and alter the electron bonds to create blue, yellow, pink and green versions.
Carbon, as present in foodstuffs such as bread and potatoes, is in hydrated form, the carbon has been chemically bonded with water and so does not appear black.
To get the black carbon back you need to remove the water, usually by heating.
This is why burnt toast is black.
Sugar is also carbon and water. But add concentrated sulphuric acid and you’ll see black carbon appear as the acid efficiently sucks out the water.
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