The Nature of Waves

A wave is any disturbance that transmits energy through matter or empty space. Most waves transfer energy by the vibration of particles in a medium. A medium is a substance through which a wave can travel. Waves that need a medium are called mechanical waves. Some waves transfer energy without going through a medium. Visible light is one example.


Types of Waves
All waves transfer energy by repeated vibrations. However, waves can differ in many ways.The two main types of waves are transverse waves and longitudinal  waves. Sometimes, a transverse wave and a longitudinal wave can combine to form another kind of wave called a surface wave.

Transverse Waves
Transverse means "moving across." Waves in which the particles vibrate in an up-and-down motion are called transverse waves. The particles in this kind of wave move across or perpendicularly to, the direction that wave is going. The highest point of a wave is called a crest, and the lowest point between each crest is called a trough, EM waves (electromagnetic waves) are considered transverse waves.


Longitudinal Waves
In a longitudinal wave, the particles of a medium vibrate back and forth along the path that the wave moves. A part of a longitudinal wave where the particles are crowded together is called a compression. A part where the particles are spread apart is called a rarefaction.

Sound Waves
A sound wave is an example of a longitudinal wave. Sound waves travel by compressions and rarefactions of air particles.


Combination of Waves
When waves form at or near the boundary between two media, a transverse wave and a longitudinal wave can combine to form a surface wave.The particles move forward at the crest of each wave and move backward and through.

Properties of Waves

Amplitude is the maximum distance that the particles of a wave’s medium vibrate from their rest position. A larger amplitude carries more energy than a wave with a small amplitude.

Wavelength is the distance between any two crests or compressions next to each other in a wave. The distance between two troughs or rarefactions next to each other is also a wavelength. The shorter  wavelength carries more energy than the wave with a longer wavelength. 

Frequency is the number of waves produced in a given amount of time. Frequency is expressed in hertz. in waves, one hertz is equal to one wave per second.

Wave Interactions

Reflection happens when a wave bounces back after hitting a barrier. all waves can be reflected. A reflected sound wave is called an echo.  Waves are not always reflected when they hit a barrier. A wave is transmitted through a substance when it passes through the substance.

Refraction is th bending of wave as the wave passes from one medium to another at an angle. When a wave moves from one medium to another, the wave's speed changes.

Diffraction is the bending of waves around a barrier or through an opening. Most of the time, waves travel in a straight line, but in some circumstances waves bend or curve when they reach the edge of an object, thus diffraction happens.

Interference

     is the combination of two or more waves that result in a single wave.

Constructive Interference happens when the crests of one wave overlap the crests of another wave or waves. The troughs of the waves also overlap. The result is a new wave that has a higher crests and deeper troughs than the original wave had.

Destructive Interference happens when the crests of one wave and troughs of another wave overlap. The new wave has smaller amplitude than the original waves had.

Standing Wave is a pattern vibration that simulates a wave that is standing still. a standing wave only looks as if its standing still.

Resonance is a phenomenon that occurs when two objects naturally vibrate at the same frequency; the sound produced by one object causes the other object to vibrate. A resonating object absorbs energy from the vibrating object and vibrates, too. 

Light

What is light?

Light is a type of energy that travels as a wave. Light is different from other waves because light is an electromagnetic wave. This is a wave that can travel through empty space or matter and consists of changing electric and magnetic field.
Electric field surrounds every charged object.  It pulls the objects that are like charges away, and pulls oppositely charged objects together. A magnetic field surrounds every magnet. It attracts all objects that contain iron.

How are EM Waves Produced?

EM waves are produced by the vibration of an electrically charged particle. When the particle vibrates, the electric field around it also vibrates, thus, a magnetic field is created.The vibration of both fields together produce an EM wave.The transfer of energy as EM waves is called radiaton.

Electromagnetic Spectrum

Characteristics of EM Waves

The entire spectrum of EM waves are called electromagnetic spectrum. It is divided into regions according to the length of the waves. There is no sharp divisions between one kind of wave and the next, some have overlapping ranges.

Microwaves have shorter wave lengths and higher frequencies than radiowaves do. Microwaves are used to send signals to other objects like cellphones and satellites.
Radars use microwaves to detect the speed and location of objects.
Infrared waves are not visible but can be detected by some devices.

What is Visible Light?

Visible light is the very narrow range of wavelengths and frequencies in the EM spectrum that humans can see. Some of the energy that reaches the earth from the sun is visible light. White light is visible light of all wavelengths combined.

Ultraviolet light is another type of EM wave produced by the sun. They affect our bodies in both good and bad ways.

Bad Effects: Too much UV light can cause
* sunburn
*wrincles, and eye damage
*skin cancer

Good Effects:
*UV lamps are made to kill bacteria on food and surgical tools.
*When exposed to UV light, skin cells produce vitamin D

X Rays and Gamma Rays

X rays can be useful in the medical field, but too much exposure can kill living cells. X ray machines are also used as security devices in airports and other public buildings. These allow officers to see inside the bags and other containers without opening them.

Gamma rays are used to treat some forms of cancer. These are also used to kill harmful bacteria in foods such as meat and fresh fruits

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Interactions of Light Waves

Reflection happens when light waves bounce off an object. The Law of Reflection states that the angle of incidence is equal to the angle of reflection. Incidence is the arrival of a beam of light at a surface.

 
Types of Reflection:

*Regular Refelction- when beams are reflected at the same angle.
*Diffuse Reflection- when beams reflect at many different angles.

Diffraction

Absorption is the transfer of energy carried by light waves to particles of matter. Scattering is an interaction of light to change direction. Refraction is the bending of a wave as it passes at an angle from one substance, or material, to another.Diffraction is the bending of waves around barriers or through openings. Interference is a wave interaction that happens when two or more waves overlap. Overlapping waves can aombine by:

*Constructive Interference- the resulting wave has greater amplitude, or height, than the individual waves had. These can be seen when light of one wavelength shines throught two small slits onto a screen.

*Deconstructive Interference- the resulting wave has smaller amplitude than the individual waves had.

Light and Color

Transmission is the passing of light through matter.

Types of matter:
*Transparent- They allow light to pass through little interference. Eg: clear glass
*Translucent- it transmits light, but also scatters it as it passes through. Eg: wax paper.
*Opaque- it is not transparent or translucent. It does not transmit any light. Eg: wood

Colors of objects are determined by the wavelengths of light that reach your eyes. ROY G. BiV (red, orange, yellow, green, blue, indigo, violet) are the colors that make up the rainbow.

Electronic Devices

Circuit Board

Electronic devices have circuit boards which is a collection of many circuit parts on a sheet of insulating material. It connects the parts of the circuit to supply electric current and send signals to the parts of the electronic device. The information sent to the device is converted into infrared light through a LED or light emitting diode.

 Many electronic devices use semiconductors which are substances that conduct an electric current better than an insulator does but not as well as a conductor does. The way a semiconductor works depends on how its electrons are arranged.

You can change the conductivity of a semiconductor through doping. It is the addition of an impurity to a semiconductor. Adding the impurity changes the arrangement of electrons.

There are 2 types of doped semiconductors:

*N-Type Semiconductor- when a replaced an atom with another atom results in an "extra" electron

*P-Type Semiconductor- when a replaced an atom with another atom results in a "hole" where an electron could be.

Joining both types of semiconductors results forms a diode. It is an electronic component that allows electric charge to move mainly in one direction. In a diode, where the two layers meet, some “extra” electrons from the n-type layer move to fill the “holes” in the p-type layer. Diodes can also change AC currents to DC by blocking one of the directions of the current.

          Transistors are electronic components that amplify or increase current It can be used in many circuits, including an amplifier and a switch. There are 2 types of transistors:

*NPN transistors- have a p-type layer in between two n-type layers.
*PNP transistors- have an n-type layer in between tow p-type layers.

An entire circuit that has many components on a single semiconductor is called an integrated circuit.

Integrated Circuit

Communication Technology

          Signal is anything, such as a movement, sound, or a set of numbers and letters, that can be used to send information. One signal is sent using another signal called a carrier. Two kinds of signals are: Analog signals, and digital signals. An analog signal is a signal whose properties change without a break or jump between values. Digital signal on the other hand is a signal that represented as a sequence of separate values.

          Radio and TV signals can either be analog or digital. An EM or electromagnetic wave is a wave that consists of changing electric and magnetic fields. They are used as carriers. Radio waves are one kind of EM wave. Radio stations use radio waves to carry signals that represent sound. They travel through the air, and are picked up by a radio antenna. The pictures we see on the screen of out televisions are made b electrons hitting the screen. Audio signals hold the information to make the sound. More and more TVs are going digital; the images and sound of these programs are much clearer than on televisions made for analog broadcasts. A plasma display do not use electron tubes, instead they have thousands of tiny cells with gases. The gases then are charged and it generates colored lights.

Computers

          Computers are electronic devices that perform tasks by following instructions given to it. The information given to the computer is called input while the final result is called an output. The computer processes the information given to it, which is called processing. This could mean adding a list of numbers, making a drawing, or even moving a piece of equipment.

          The first computer was called the ENIAC (Electronic Numeral Integrator and Computer). This computer is much larger than what we use today. The modern computers use microprocessors which are single semiconductor chips that control and execute a microcomputer’s instructions. Computer hardware is the parts or pieces of equipment that make up a computer. These are composed of:

*Input device- gives information, or input to the computer.

*Central processing unit- is the microprocessor; processing on the spot for storage in memory.

*Memory- used to store information.

          *ROM- is the permanent memory such as maintenance, hardware        management, and Start-ups. It cannot be changed or added to.
          *RAM- is the temporary memory. The information is lost when the power is shut off.

*Output device- such as printers, monitors, speakers etc.

Computer Software is a set of instructions or commands that tells a computer what to do. A computer program is software.

There are two kinds of software:

*Operating-system software- handles basic operations needed by the computer
*Application software- tells the computer to run a utility

The internet is a huge computer network made up of millions of computers that can all share information.  Part of the internet is called the WWW or world wide web.

Electromagnetism

Magnets are any materials that attracts iron, or any materials containing iron. The magnetic poles of a magnet are the points on a magnet that have opposite magnetic qualities. These are the north and south poles. Magnets also have magnetic force, it is the force of the attraction or repulsion generated by moving or spinning electric charges. Every magnet has it's own magnetic field which exists in the region around a magnet in which magnetic forces can act.

Electromagnetism is the interaction between electricity and magnetism. This could be explained by Hans Oersted's experiment. A coil of wire that produces a magnetic field when carrying an electric current is called a solenoid. The strength of the magnetic field of a solenoid increases as more loops per meter are used.  An electromagnet is a coil that has a soft iron core and that acts as a magnet with an electric current in the coil. The magnetic field of a an electromagnet is the field of the solenoid plus the field of the magnetized core. Thus, the magnetic field of an electromagnet may be hundreds of times stronger than the field of just the solenoid.

Electricity

         Electricity follows the law of electric charges that states: Like charges repel and opposite charges attract. The force between charged objects is an electric force.


The strength of Electric force is affected by two factors:
* The amount of charge on each object, the greater its charge, the greater the electric force is.
* The distance between the charges; the closer they are, the greater the electric force.
        
        Charged things are affected by electric force because charged things have an electric field. An electric field is the region around a charged object in which an electric force is exerted on another charged object.


Charging an object can be done through:
* Friction- when an object is "wiped" or "rubbed" from an object onto another.
* Conduction- when electrons move from one object to another by direct contact.
* Induction- when charges in uncharged metal object are rearranged without direct contact with a charged object.


      When you charge an object by any method, no charges are created nor destroyed. The number of protons and electrons stay the same. Electrons simply move from one atom to another, and it then creates difference of charge.This is then the conservation of charge.

      
 An electrical conductor is a material in which charges move easily. While an electrical insulator is a material in which charges cannot move easily. 


Static electricity is the electric charge that is stored. When charged objects find a way to release the energy, this then is called electric discharge. An example of electric discharge is lightning. 
    
  An electric current is the rate at which electricity flows at a given point to another. Two types of electric current are: alternating current (it flows in one direction then flows in the opposite direction, thus flows in two directions) and direct current (flows in on direction only). While voltage is the potential difference in electrical charge between two points in an electric field. The opposition to the flow of the current is called resistance. The relationship between voltage, current and resistance is shown by the Ohm's Law.

The formulas of Ohm's Law are:

* VOLTAGE = CURRENT x RESISTANCE
   V= I x R


*CURRENT = VOLTAGE/RESISTANCE
    I= V/R


* RESISTANCE = VOLTAGE/CURRENT
    R=V/I


Electric circuits 
   There are two types of circuits. The Parallel Circuit- the same voltage is applied to the components in a parallel circuit. The second one is Series Circuit- the current in the series passes through all the components in the circuit, therefore the components in the circuit carry the same current.
     

Radioactivity

Our topic was about Radioactivity.

 In radioactivity, obviously there is radiation; is the process of emitting energy in forms of waves or particles. Radiation is produced when particles interact or decay (emission of particles from isotopes).
Fact: A large contribution of radiation is from the sun (solar) or from radioactive isotopes of the elements (terrestrial)

  The three types of radiation are:
    

 *Alpha - is a kind of decay that gives off protons and neutrons, resulting in a different substance. Alpha particles are positively charged.
   
 * Beta- is a kind of decay that gives off positron and electrons, thus makes it negatively charged.

 *Gamma-rays- is a high energy light particle.Gamma-rays are the released energy after alpha and beta decay. It is also the deadliest ray.

Half-life is how long it takes for half of a sample of a radioactive substances to undergo radioactive decay.

Chemical Compounds

Last week our topic was about Chemical Compounds. So basically, chemical compound is a pure chemical substance that can be divided into smaller substances. It occurs through Chemical bonds which occurs between valence electrons. It is divided into forms of compounds: Ionic, Covalent, and Organic Compound. Ionic compounds are formed through the reaction of metals and non-metals. Ionic compounds have Ions; when Hydronium ions increase when dissolved in water, it then forms Acids. Acids are used as cleaning agents, decorations, vitamins, and flavoring in sodas. When Hydroxide ions increase, it forms Bases. When Acids and Bases react to one another, it forms the Neutralization Reaction. Then we have Covalent Compounds. Covalent Compounds are formed through covalent bonds (the sharing of an electron). Then Organic Compounds are compounds which have carbon atoms. A substance that has one Carbon atom and Hydrogen atom are called Hydrocarbons. There are four types of Hydrocarbons. Alkane, Alkene, Alkyne, and Unsaturated Hydrocarbon. Orgainc compounds that are made by humans are called Biochemicals. Biochemicals that do not dissolve in water are called Lipids.