## Monday, January 31, 2011

### WAVE

1. Waves are produced by vibrating systems.

Vibrating systems

2. Waves transfer energy. Waves that travel through a medium transfer energy without transferring matter.

3. In transverse waves, the direction of waves propagation is perpendicular to the direction of vibration of the particles.
Example: water waves, light waves and electromagnetic waves.

4. In longitudinal waves, the direction of wave propagation is parallel to the direction of vibration of the particles.
Longitudinal waves need a medium to propagate. This type of waves cannot propagate through a vacuum.
Example: a sound wave.

5. A wavefront is an imaginary line representing all parts of a wave in which particles are vibrating in the same phase and have the same distance from the source.
The direction of propagation of waves is always perpendicular to the wavefront.

6. Amplitude, a, is the maximum displacement from the equilibrium position.

7. Period, T, is the time required to make one complete oscillation.

8. Frequency, f, is the number of complete oscillations made in one second.

9. Wavelength, is defined as the distance between two consecutive points that are in phase.

( i ) For a transverse wave, wavelength can be measured as the distance from one crest and also the distance from one trough to the next trough.
(ii ) For a longitudinal wave, wavelength can be measured as the distance between
two consecutive compressions or two consecutive rarefactions.

### Displacement- Time graph and displacement -Distance Graph for a wave

The sinusoidal graph shown is a graph of displacement, s against time , t of a load on a spring.

O is called the equilibrium position.

From a displacement-time graph for a wave, we can obtain
i) amplitude, a ,and
ii) period, T.

From a displacement- distance graph for a wave, we can obtain
i) amplitude, a ,and
ii) wavelength, λ

Relationship between Speed, (v) Wavelength,(λ) and Frequency (f)

The speed of a wave is determined by its wavelength, λ, and its frequency, f , according ti the equation V= f λ

For a wave moving at constant speed, increasing the frequency will result in a decrease in the wavelength.

For a wave moving at constant speed, decreasing the frequency will result in an increase in the wavelength.

Work example:

What is the frequency of water waves with the wavelength of 3.0 cm and traveling at a speed of 1.5 cm/s ?

solution :

Step 1: write formula first
V= f λ

step 2 : Substitute all given info into formula
1.5
cm/s = f x 3.0 cm

Step 3:find unknown
f = 0.5 Hz

### Reflection of waves

Reflection of a wave occurs when a wave strikes an obstacle. The wave undergoes a change in direction of propagation when it is reflected.

The phenomenon of reflection of waves obeys the Law of reflection where:
1. The angle of reflection is notequal to the angle of incidence.
2. The incident wave, the reflected wave and normal lie in the same plane which is perpendicular to the reflecting surface at the point of incidence.

Characteristics of reflection of waves:
1. The wavelength , speed and frequency of the reflected waves is the same as that of the incidence.
2. Angle of incidence = angle of reflection.
3. Direction of propagation of wave changes.

Application of reflection of waves:

2. Makeup mirror
3. Car rear mirror and side mirror for your safety .
4. Optical fibre
5. Ultrasonic
6. Fishing with sonar.
7. Seawall to deflected the energy of the waves from the coast.

### CHAPTER 1 & 2 - Introduction of Physics & Forces and Motion

· Velocity : Rate of displacement

· Accelaration : Rate of change of velocity

· Momentum : Product mass and velocity

· Impuls : Change of momentum

· Impulsive Force : Rate of Change of momentum in short interval

· Free Fall : the object fall under gravitional force only

· Elasticity : return to its original length when force acting removed

· Principle of conservation of energy : energy cannot be created or destroyed but it can be transferred from one form to another

· Hooke Law : The extension or compression of a spring is direct proportional to the applied force until the elastic limit is not exceed.

· Zero errors occurs when the instrument gives a non- zero reading when in fact the actual reading is zero.

· Parralax error : error in reading / observer eye is not perpendicular to the scale

· Base Quantities : The physical quantities which are used as the basis for the measurement and can’t be derived from other physical quantities.

· Physical quantities are quantities that can be measured

· Derived Quantities :The physical quantities which were derived from base quantities by multiplication operation or division operation or both

· A scalar is any quantity with size (magnitude) but without specified direction.

· A vector is any quantity with size (magnitude) and specified direction.

· Accuracy is the degree of closeness of the measurements to the actual or accepted value.

· Sensitivity is the degree of a measuring instrument to record small change in its reading.

· Systematic errors are errors in the measurement of a physical quantity due to instruments, the effects of surrounding conditions and physical constraints of the observer.

### CHAPTER 3 - DEFINITION

- Density : is the mass per volume

- Pascal Principle : In the closed fluid system, an external applied force is transmitted uniformly in all direction.

- Archimedes Principle : upward bouyant force an a submerged object is equal to the weight of the fluid displaced by

the object.

- Pressure : Force per unit area

- Density is mass per volume of the material

### CHAPTER 4 - DEFINITION

- Thermal equlibrium : When two object in thermal contact , no net heat energy transfer between each other/ rate of heat transfer is same between each other, same temperature.

- Specific heat capacity : heat energy required to increase temperature 1 C for 1 kg substance.

- Specific latent heat of fusion: quantity heat energy required to change 1 kg of a substance from solid to liquid without a change of temperature

- Specific latent heat of vapourisation: quantity heat energy required to change 1 kg of a substance from liquid to gas without a change of temperature

- Temperature : Degree of hotness of a body

- Heat : Form of energy that tranfer from hot body to cold body

### CHAPTER 5 - DEFINITION

- Real Image : Image can be seen on the screen

- Virtual Image : Image is not form on the screen

- Critical angle : Angle of incidence when angle of refraction 90

### CHAPTER 6 - DEFINITION

- coherent waves : The waves that have same frequency and same phase

### CHAPTER 7 - DEFINITION

- 20W , 240V : the eletrical appliances use 240 potential difference/ voltage will release energy 20J in 1 second.

- Current : The rate of flow of charge

### CHAPTER 8 - DEFINITION

- Magnetic field : the region is under magnetic force

### CHAPTER 9 - DEFINITION

- Semiconductor : A conductivity between a conductor and insulator

### CHAPTER 10 - DEFINITION

- Half life : Time for activity of radioisotope element reduce to half its original value

- Radioisotope : Isotope that are not stable

### PHYSIC CHAPTER FOR FORM 4

CHAPTER 1

Introduction in Physics

- Basic and Derived quantities

- Unit conversion

- Scientific investigation

- Graph plotting & Graph interpretation

- Vernier Caliper

- Micrometer Screw Gauge

- Sensitivity , Precision // consistency , accuracy

- Error

CHAPTER 2

Force & Motion

- Displacement-time & velocity-time graph

- Linear Motion using ticker timer

- Inertia

- Momentum

- Impulsive force

- Force in equilibriumn, nett force , resultant force

- Pulley system

- Lift system

- Gravity Force // Types of force

- Kinetic Energy & Gravity potential Energy // work

- Elasticity // Hooke Laws

CHAPTER 3

Force & Pressure

- Solid Pressure

- Liquid Pressure

- Gas & atmospheric pressure

- Pascal Principle

- Achimedes Principle

- Bernoulli Principle

CHAPTER 4

Heat

- Heat energy & Temperature

- Thermal Equilibrium

- Specific Heat capacity // Water // aluminium

- Specific latent heat of fusion // Latent heat of vapourisation

- Temperature-time graph // calculation

- Gas Laws // Absolute zero // Kelvin

CHAPTER 5

Light

- Reflection of mirror // Laws of reflection

- Concave mirror // convex mirror // ray diagrams

- Refraction of transparent materials

## Sunday, January 30, 2011

### 1.1 Understanding Physics

In physics, we study natural phenomena and the properties of matter.
The aim of physics is to explain the fundamental nature of the universe by using the concept of physics.
Physics involves the conduct of studies and experiments to find answers to the question ‘Why?’and ‘How?’ in relation to the mysteries of the universe.
The majority of natural phenomena can be explained using the principles of physics, for example;
i) Shadows are formed because light travel in straight line.
ii) Black objects are black because almost all the light that falls on them is absorbed.

Fields of study in physics
1. Force and motion - investigates the action of force and motion.
2. Forces and pressure- pressure, pressure in liquids, gas pressure, atmospheric pressure, Pascal’s principle, Archimedes’ principle, Bernoulli’s principle.
3. Heat- Studies the influence of heat on different types of matter.
4. Light - explains the different phenomenon due to light.
5. Electricity and electromagnetism- investigates the interactions of electric and magnetic fields.
6. Electronics - studies the use of electronic devices in various field.
7. Waves - understands the properties of different types of waves and their uses

## Friday, January 28, 2011

### TAHNIAH

Tahniah kepada Cikgu Azhar Bin Bakhori kerana telah mendapat Anugerah Perkhidmatan Cemerlang (APC) dan mendapat Anugerah Guru Cemerlang (GC 44) berkuatkuasa 24 ogos 2010.
Moga dapat memberi komitmen yang konsistent dalam bidang Pengajaran dan Pembelajaran bagi subjek Fizik dan Sains.