1.They are produced bythe negative electrode, or cathode,and travel towards the anode.
2.Theytravel in straight lines and produce sharp shadows.When an opaque object like a metal cross is placed in the path of cathode rays in a discharge tube, a shadow of the metal cross is formed at the end opposite to the cathode.
3.Theyhave energy and can do work thus produce a mechanical effects On a light paddle in the path of cathode rays that the blades of the paddle wheel will rotate. This shows that cathode rays are a beam of particles having mass and possessing kinetic energy.
4.They are deflected by electric and magnetic fields and have a negative charge. Are Negatively ChargedWhen an electric field is applied in the path of cathode rays, they are deflected towards the positive plate of the electric field, which shows cathode rays are made up of negatively charged particles.
5.They are beams of tiny, negatively charged particles called electrons.
1.John Dalton proposed that matter is made of atoms. All substances were either made of single atoms or combinations of atoms (molecules).
2.He thought that atoms were indivisible/undivided.
3.But In the 19th century, experiments showed that atoms were divisible. As a result, new particles and forces were found.
4.J.J Thompson suggested that,atom was consists of sub unit particle which is 1,000 smalller than atom itself.
5.This particle was called as an electron and was the first atomic particle to be discovered by scientists.
6.Before the experimentation by Thompson,William Crookes had carried out an experiment to study the behaviour of metals heated in a vacuum.
7.The experiment of Crookes showed that,a heated cathode produced a stream of radiation, which cause gases at low pressure to glow. This also was proved as many Physicists in the 19th century found out that if they constructed a glass tube with wires inserted in both ends, and pumped out as much of the air as they could, an electric charge passed across the tube from the wires would create a fluorescent glow.Figure 1
8.The radiation emitted from the cathode was given the name 'Cathode rays'.
9.Thomson discovered the electron through his explorations on the properties of cathode rays.
10.A common discharge tube is a glass tube having two metal plates (electrodes of cathode and anode). It has a side tube through which air can be pumped out by using a vacuum pump, so that experiments can be performed at low pressure.
11.Cathode rays was also known as Electron beam / e-beam.It is a stream of electron observed in vacum. Cathode rays are also so named because they are emitted by the negative electrode, or cathode, in a vacuum tube .
12.Electrons were first discovered as the part of cathode rays. The development of television systems was based on the development of the cathode ray tube (CRT). The first cathode ray tube was invented by the German scientist Karl Ferdinand Braun in 1897.
1.A purechemical substanceconsisting of one type ofatom that every different element is distinguished by itsatomic number, which is the number ofprotonsin itsnucleus.
2.As of May 2011, 118 elements have been identified, the latest beingununoctium in 2002.
Ununoctium – it is a temporary name with temporary element Uuo by IUPAC.
IUPAC -International Union of Pure Applied Chemistry is an international standard for chemistry.But besides IUPAC we also have IUPAP International Union of Pure and Applied Physics,both,are the members of International Council for Science(ICSU).The international headquarters of IUPAC is located inZürich,Switzerland.Itwas first addressed in 1860 by German scientist.
3.Of the 118 known elements, only the first 94 are believed to occur naturally onEarth. Of these naturally occurring elements, 80 are stable or essentially so, while the others are radioactive, decaying into other.See figure below :
4.The number ofnucleons(protons and neutrons) in thenucleus, = themass number.It is not same between two isotopes. For example,carbon-12,carbon-13andcarbon-14are three isotopes of the elementcarbonwith mass numbers 12, 13 and 14 respectively.
5.Theatomic numberof carbon is 6 (every carbon atom has 6 protons); therefore theneutron numbersin these isotopes are 6, 7 and 8 respectively.
- consist entirely of numbers and are almost impossible for humans to read and write.
ii.Assembly language/ low level language
- Assembly languages have the same structure and set ofcommandsas machine languages, but they enable aprogrammerto usenamesinstead of numbers.
Example assembly language
iii. High level language
-high-level language is called so because they are closer to human languages and further frommachine languages. In contrast,assembly languagesare considered low-level because they are very close to machine languages.
-The main advantage of high-level languages overlow-level languagesis that they are easier to read, write, and maintain. Ultimately, programs written in a high-level language must be translated into machine language.
-There are two ways torunprograms written in a high-level language. The most common is by using compiler,; the other method is to pass the program through an interpreter.
2.The storage capacity (example,256 MB,1GB,2GB etc ) indicates the number of bytes it can hold.
3.Computer data is using binary system that consists of ones and zeros in a string or line.
4. Each string has eight set of binary number (zeros and ones) that we call them as bits.Meaning,1 string = 8 bits.
5. 8 bits = 1 Bytes
6.Example,00000100 = 1Byte
7.1 Byte = 1 Character.
8.Example,the capital letter "K" is expressed in binary system as 01001011.
9.1 Bytes is the smallest amount of transfer.
10.Example,a Gif image with 4 kB,equal to 4 kilo bytes (4000) bytes.Meaning,it has 4000 thousand set of string,with 8 bits each string.Example :
00000001
00000010
00000100
00001000
.
.
.
.
.
(until 4000 strings)
Hence,4000 strings (bytes) x 8 bits = 32,000 thousands of bits (0 and 1) for single gif image.
11.Do remember that,KB = Kilo Byte and Kb=Kilo bits.
12.A kB is 8 times larger than kb.Why,kb = 1000 bits,while kB = 1000 (00000000).
13.Mathematically,1 kB = 1000 bytes.Actually, 1 kB is not equal to 1000,but 1024.This is because,mostly computer memory used traditional measurement instead of modern measurement aka SI units aka Metrix system.
14.See below,traditional and modern measurement:
Figure 1 : indicates the traditional measurement that widely used in memory system.
Figure 2 : the green marks indicate the traditional measurement.While white marks indicate the SI standard that we commonly used in life.
Under the topic,we will cover several aspects,they are,
1. Hardware
2. Software
3. Computer and its components
4. an operating system
1.Hardware
Refers to objects that we can actually see and touch, likedisks,display screens,keyboards,printers,processor,memory andchips.Refer figure 1 and 2
Figure 1 : Refer to figure,system unit also called peripheral device.
Figure 2 : shows,an example of hardware (hard disk).Everything that's currently "in the computer" is actually stored on that hard disk
2.Software
In contrast,softwareis untouchable. Software exists as ideas, concepts, and symbols.Examples,microsoft word,internet explorer.Handphone,Atm machine is an example of applications developed using proggraming language.
3.Computer and its components
a. Central processing unit /CPU /processor.
Two type of processor : i. ALU /Aritmethic Logic Unit - performs arithmetic (addressing 4 basic operations,addition,substraction,multiply,division with integers,real number etc )and logical operations. ii. CU / Control Unit - extractsinstructionsfrommemoryand decodes
b. Memory.
Memory can refer to many types of memory within computer,but normally we refered to RAM / Random acces memory There's too much "stuff" on our computer's hard disk to use it all at the same time. During the session sitting in front of the computer, we will probably use only a small amount of all that's available. The stuff we working with at given moment is stored in random access memory (often abbreviated RAM).
So if RAM is so fast, why not we put everything in it? Why have a hard disk at all? The answer to that lies in the fact that RAM is volatile. As soon as the computer is shut off, whether intentionally or by an accidental power outage, every thing in RAM disappears, just as quickly as a light bulb goes out when the plug is pulled. So you don't want to rely on RAM to hold everything. A disk, on the other hand, holds its information whether the power is on or off.
Hence,all the information is stored on our computer'shard disk. we will never see the actual hard disk because it's sealed inside a special housing and needs to stay that way. Unlike RAM, which is volatile, the hard disk can hold information forever -- with or without electricity.
When we use alphaneumeric (combination of alphabet and numbers ) ,it should not beginning with digit.But must be started with alphabet.
Example :
As we write 2b,mathematica will show us “2 b”,with spacing in the middle.This infact, “2 b” = 2xb.The correct way to use alphaneumeric is b2 instead of 2b
2. Exponentiation Exponention is represented by using ^,hence,x^y means : 3.Semicolon Semicolon ie ; can avoid mathematica from showing the result of each calculation.Example: a=4 after (shift+enter) 4 a=3 after (shift +enter) 3 c = a + b 7 The number 4 and 3 above can be avoided from display by mathematica by adding semicolon.See example below: a=4; b=3; c=a+b 7 4. Use parenthese for modofication Example:2+3*5 = 17 (this follows the standard operation,multiply first followed by plus operation) However,we can modify this by adding a parenthese bracket.Dont use square or round bracket. Example : (2+3)*5 = 25 5.N expression a. N[expression] - gives the approximation to 6 significant digits (mathematica's default) Example : N[Pi] 3.14159 b.N[expression,n] - an approximation accurate to n significants digits. N[Pai,50] 3.1231456758697087867543213245
