hydrocarbons

Organic compounds consisting of carbon and hydrogen are called hydrocarbons. They are the simplest form of the organic compounds. Hydrocarbons are regarded as the parent family of organic compounds because other various organic compounds may be synthesized from hydrocarbons through chemical process by replacement of one or many hydrogen atoms by functional groups.
The main sources of organic compounds are coal and petroleum since they are byproducts of living organisms like plant and animals i.e. both are considered to be of biological origin. Petroleum is commonly called rock oil. In Greek, Petra stands for rock and oleum stands for oil. Thus coal and petroleum are naturally occurring sources of hydrocarbons. Lower hydrocarbons like methane, ethane, propane etc are present in natural gases which are mainly obtained from petrol. Coal is the chief sources of aromatic hydrocarbons. Thus naturally occurring fossils like petroleum and coal are the major sources of different hydrocarbons. Aliphatic hydrocarbons are mostly obtained from petroleum whereas aromatic hydrocarbons are extracted from coal.

magnetism

Magnet was 1st discovered in ancient Asia Minor. The word ‘magnet’ is derived from ‘magnesia’. In ancient times, the Greek had seen a certain stone possessing the properties of attracting small pieces of iron, the stone was typically black. Chemically it consisted of iron oxide (Fe3O4 ) called ‘magnetite’. The ore ‘magnetite’ is called magnet because it has the property of attracting iron. The property of magnet by virtue of which it can attract a piece of iron is called magnetism. When this stone is suspended freely, it sets itself pointing north and south directions. This is the directive property of magnet. Ancient Chinese used this property to guide their ships in oceans. So this stone was named as “lode stone” or “leading stone”. Nowadays many artificial magnets are made from iron or steel.
A magnet has a property of attracting small pieces towards it. When a bar magnet is dipped inside iron fillings, it is found that the ends of this magnet attract more iron fillings than the middle part of it. So, it is clear that in middle part, attraction is poor where as part close to two ends has maximum attractive property.

optics

Optics is the branch of physics which deals with the nature and propagation of light, including refraction, dispersion and wave property of light such as interference, diffraction, and polarization. Light is a form of energy. It can be divided into two categories: visible and invisible light. The visible light on entering our eyes produces the sensation of sight. But light in the invisible region doesn’t produce sensation of sight. Any object that emits light is called source of light. There are two sources of light :(a) self-luminous: an object which possesses light of its own is called self-luminous. E.g.: sun, stars, candle, glowing electric bulbs etc. (b) non-luminous: It is the source of light which doesn’t possesses light of its own but it receives light from other sources and then reflects or scatters to the surroundings. E.g.: moon, planets, book, papers etc.
Any substances through which light passes (or propagate) is called medium.eg: water, glass, plastic, etc. the along which light travels is called a ray. The combination of number of rays is called beam. If a light ray is reversed, it always travels along its original path. Thus optics is branch of science which is very useful in our daily life.

measurement

MEASUREMENTS
“When you can measure what you are talking about and express it in numbers you know something about it, but when you cannot, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the stage of a science, whatever the matter be.” This is the saying of Lord Kelvin. In physics, all the measurable quantities are referred to as physical quantities. These quantities characterize physical properties of matter. Length, mass, time, speed, temperature, displacement etc are few examples of physical quantities.
The physical quantities which are independent of other physical quantities are known as basic or fundamental quantities. All then other physical quantities derived with help of these basic quantities are known as derived quantities. Any standard chosen unit demands the following physical characteristics as it should be accessible, invariable and easily reproducible.

physical phenomenon

“Physics” is derived from a Greek word ‘physis’ which means ‘nature’. Thus Physics is a branch of science which deals with the study of natural phenomenon. Therefore, it was also known as natural philosophy which would study the entire natural science including Astronomy and Chemistry. Nowadays, Physics means only that branch of science which deals with the properties of matter, energy and relationship between them. It is the most basic science.
Physics is not only wide but it is also an interesting and exciting subject. The ranges of mass, length and time concerned with this subject are very large. It is amazingly interesting that in spite of this complex and wide range of these phenomenon, many of these can be explained forming a few basic laws and principles. Although a large number of parameters are associated with a complex physical phenomenon, many of them are less important to explain the phenomenon under study. Thus because of physics, it becomes possible to uncover the hidden simplicity within a complex phenomenon of nature.

Low diversification in the Cretaceous

Statistical analyses based on raw data suggest that dinosaurs diversified, i.e. the number of species increased, in the Late Cretaceous. However in July 2008 Graeme T. Lloyd et al. argued that this apparent diversification was an illusion caused by sampling bias, because Late Cretaceous rocks have been very heavily studied. Instead, they wrote, dinosaurs underwent only two significant diversifications in the Late Cretaceous, the initial radiations of the euhadrosaurs and ceratopsians. In the Mid Cretaceous, the flowering angiosperm plants became a major part of terrestrial ecosystems, which had previous been dominated by gymnosperms such as conifers. Dinosaur coprolites (fossilized dung) indicate that, while some ate angiosperms, most herbivorous dinosaurs mainly ate gymnosperms. Meanwhile herbivorous insects and mammals diversified rapidly to take advantage of the new type of plant food, while lizards, snakes, crocodilians and birds also diversified at the same time. Lloyd et al. suggest that dinosaurs' failure to diversify as ecosystems were changing doomed them to extinction.