NATURE OF LIGHT

Newton’s corpuscular theory of light
Newton’s corpuscular theory of light is based on the following points 1. Light consists of very tiny particles known as “corpuscular”. 2. These corpuscles on emission from the source of light travel in straight line with high velocity 3. When these particles enter the eyes, they produce image of the object or sensation of vision. 4. Corpuscles of different colours have different sizes.
Huygen’s wave theory of light
In 1679, Christian Huygens proposed the wave theory of light. According to huygen’s wave theory: 1. Each point in a source of light sends out waves in all directions in hypothetical medium called "ETHER". 2. Light is a form of energy 3. Light travels in the form of waves. 4. A medium is necessary for the propagation of waves & the whole space is filled with an imaginary medium called Ether 5. Light waves have very short wave length
Quantum theory of light
Quantum theory was put forward by MAX-PLANCK in 1905. According to quantum theory “Energy radiated or absorbed can not have any fractional value. This energy must be an integral multiple of a fixed quantity of energy. This quantity is called “QUANTUM” OR Energy released or absorbed is always in the form of packets of energy or bundles of energy. These packets of energy are known as QUANTA or PHOTONS

MACHINES

MACHINE
A machine is a device by means of which work can be performed easily or in a convenient manner. A machine can be used :  To lift heavy loads by applying little force.  To enlarge magnitude of force  To increase rate of work done  To change the direction of force Example of simple machines are : Lever, pulley, inclined plane, wedge, screw etc.
EFFORT OR POWER
The power directly applied to a machine to lift a load is called Effort or Power. It is denoted by ‘P’.
LOAD OR WEIGHT
The weight lifted by a machine is called Load. It is denoted by ‘W’.
MECHANICAL ADVANTAGE
The ratio of weight (load) lifted by a machine to the force(effort) applied on a machine is called mechanical advantage of the machine. Greater the value of mechanical advantage of a machine, more easier is the work done. Mathematically,
M.A = load/effort
OR
M.A = W/P
UNIT:
It has no unit.
INPUT
Amount of work done on a machine by a given effort (force) is called input of a machine.
Input = effort x distance through which effort acts OR
input = P x d
OUTPUT
Amount of work done by a machine on the load (weight) is called output of the machine.
Output = load x distance covered by the load OR
Output = W x D
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EFFICIENCY
The ratio of output of a machine to the input of machine is called its efficiency.
h = output/input h = (W x D)/(P x d) Efficiency in %:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         h = (W x D)/(P x d )x100
UNIT:
It has no unit.
IDEAL MACHINE
An ideal machine is a hypothetical machine whose output is equal to its input. For an ideal machine
output = input
Efficiency of an ideal machine is 100% because there is no loss of energy in an ideal machine due to friction or any other means that can waste useful energy.
M.A of an ideal machine is d / h.
LEVER
Lever is a simple machine which is used to lift heavy bodies or heavy load in a very easy way. Lever consists of a rigid bar capable to rotate about a fixed axis called fulcrum. Effort is applied at one end of the bar and weight can be lifted from the other end.
TYPES OF LEVER
There are three kinds of lever depending upon the positions of load , effort and fulcrum.
FIRST KIND OF LEVER
In the first kind of lever, the fulcrum F lies between effort (P) and load (W).
Example: common balance, seesaw, scissors, handle of hand pump.
SECOND KIND OF LEVER
In the second kind of lever, load (W) lies between effort (P) and fulcrum (F).
Example: door, nutcracker, punching machine.
THIRD KIND OF LEVER
In the third kind of lever, effort (P) lies between load (W) and fulcrum (F). Example: forceps, jaws, human forearm, firetong.

DISTRIBUTIVE LAW FOR DOT PRODUCT

DISTRIBUTIVE LAW FOR DOT PRODUCT
According to distributive law for dot product:
	PROOF
	Consider three vectors , and .Here we will use geometric interpretation of dot product by drawing projection as shown below. First we obtain the sum of vectors  and by head to tail rule then we draw projection  and from the terminal point of vector respectively onto the direction of . The dot product  is equal to the projection of vector  onto the direction of  multiplied by the magnitude of. i.e.

Chemistry Notes and Review

Atomic and Molecular Structure

The building blocks of matter are atoms, which join together to form molecules or compounds. It's important to know the parts of an atom, what ions and isotopes are, and how atoms join together.

Parts of an Atom

Atoms are made up of three components:

• protons - positive electric charge
• neutrons - no electric charge
• electrons - negative electric charge

Protons and neutrons form the nucleus or center of each atom. Electrons orbit the nucleus. So, the nucleus of each atom has a net positive charge, while the outer portion of the atom has a net negative charge. In chemical reactions, atoms lose, gain, or share electrons. The nucleus does not participate in ordinary chemical reactions, although nuclear decay and nuclear reactions can cause changes in the atomic nucleus.

Atoms, Ions, and Isotopes

The number of protons in an atom determines which element it is. Each element has a one- or two-letter symbol that is used to identify it in chemical formulas and reactions. The symbol for helium is He. An atom with two protons is a helium atom regardless of how many neutrons or electrons it has. An atom may have the same number of protons, neutrons, and electrons or the number of neutrons and/or electron may differ from the number of protons.

Atoms that carry a net positive or negative electric charge are ions. For example, if a helium atom loses two electrons, it would have a net charge of +2, which would be written He2+.

Varying the number of neutrons in an atom determines which isotope of a element it is. Atoms may be written with nuclear symbols to identify their isotope, where the number of nucleons (protons plus neutrons) is listed above and to the left of an element symbol, with the number of protons listed below and to the left of the symbol. For example, three isotopes of hydrogen are:

11H, 21H, 31H

Since you know the number of protons never changes for an atom of an element, isotopes more commonly are written using the element symbol and the number of nucleons. For example, you could write H-1, H-2, and H-3 for the three isotopes of hydrogen or U-236 and U-238 for two common isotopes of uranium.

Atomic Number and Atomic Weight

The atomic number of an atom identifies its element and its number of protons. The atomic weight is the number of protons plus the number of neutrons in an element (because the mass of electrons is so small compared with that of protons and neutrons that it essentially doesn't count). The atomic weight sometimes is called atomic mass or the atomic mass number. The atomic number of helium is 2. The atomic weight of helium is 4. Note that the atomic mass of an element on the periodic table isn't a whole number. For example, the atomic mass of helium is given as 4.003 rather than 4. This is because the periodic table reflects the natural abundance of isotopes of an element. In chemistry calculations, you use the atomic mass given on the periodic table, assuming a sample of an element reflects the natural range of isotopes for that element.

Molecules

Atoms interact with each other, often forming chemical bonds with each other. When two or more atoms bond to each other, they form a molecule. A molecule can be simple, such as H2, or more complex, such as C6H12O6. The subscripts indicate the number of each type of atom in a molecule. The first example describes an molecule formed by two atoms of hydrogen. The second example describes a molecule formed by 6 atoms of carbon, 12 atoms of hydrogen, and 6 atoms of oxygen. While you could write the atoms in any order, the convention is to write the positively charged past of a molecule first, followed by the negatively charged part of the molecule. So, sodium chloride is written NaCl and not ClNa.