Thursday, March 12, 2009

KEPUTUSAN SPM 2008

PELAJAR TERBAIK EMPAYAR MAAHAD

13A

AFNAN
SYIHAM
AIMAT
ZULFADLI

Tahniah diucapkan kepada mereka semua kerana telah berjaya menaikkan martabat Empayar Maahad.

InsyaALLAH SPM 2009 bakal mencatatkan rekod yang baik daripada tahun-tahun yang lalu bersempena dengan Program Maahad Gemilang.

MAAHAD GEMILANG DIPELOPORI KERAJAAN DAMASCUS V

Friday, March 6, 2009

Reflection and Refraction

Reflection

Waves (and in particular light) is reflected off of surfaces. If we take the example of rays of light on a mirror, a virtual image is formed. This is upright, the same size, and appears to be directly behind the mirror.

If a ray of light is beamed at a mirror, this will be reflected. The normal to the block is perpendicular to it, the angles are measured in reference to this. The ray going in is called the incident ray and the acute (smaller) angle it makes with the normal is called the angle of incidence. See diagram below to understand this.


The angle the reflected ray leaves is equal to the angle of incidence. I.e. angle of incidence = angle of reflection.


Refraction

Refraction has light waves changing direction. This occurs as a result of the light changing speed when it goes from one medium to another. The speed of light varies according to what it is travelling through, the standard given is the speed in a vacuum, this is 299 792 Km/s, the speed of light in water is 225 000 Km/s.

Take a look at the example of refraction shown below. The light ray is travelling through tank of water.



When the light enters the water, it slows down so moves towards the normal. When the light emerges from the tank into air, it speeds up so it moves away from the normal.

Refraction in water is the reason that when you stand beside a swimming pool and look down at it, it appears to be shallower than it really is. Also, if you put a straw at an angle in a cup of water (or juice or whatever), it will appear to bend at the water-air boundary.

Total Internal Reflection (TIR)

The inner surface of a glass block will begin acting like a mirror if a ray of light strikes it at the critical angle, this is 42°. This value is less in other mediums, for instance it is 49° between water and air.

When the angle of incidence is equal to the critical angle, the light will emerge along the edge of the block, but when the angle of incidence is more than the critical angle, it will be reflected. The diagram below illustrates this.



This phenomenon is put into practical use in fibre optic cables. Where light signals will travel along a glass fibre providing the angle of incidence exceeds the critical angle of 42°. Fibre optic cables are used to send telecommunication information such as the internet.

Sound

Sound Waves

Sound waves are longitudinal waves and can be reflected, refracted and diffracted like all waves. They are mechanical vibrations of particles that can be detected by the human ear.

When a sound wave is reflected we call it an echo. Echoes of ultrasound are used by bats and sonar, to detect the position of things.

A sound wave can be represented as a sine curve; by altering its amplitude and frequency, we can change the sound.



If the amplitude is increased, the sound gets lounder - so a higher volume. If the frequency is increased, you get a higher pitched sound. Humans can only hear sounds that are in a certain range of frequencies, this is generally 20 to 20 000 Hz, but perception of sounds at the upper end reduced with age. Sounds that are above 20 000Hz are said to be ultrasonic.

Ultrasound

Humans can hear within the 20 to 20 000Hz range. Other animals have much higher ranges of hearing: dogs can hear up to 45 000 Hz, cats up to 64 000Hz and the bat up to 110 000 Hz. Some animals also have ranges of hearing much smaller than humans: the chicken has a range of 125 - 2000Hz.

Ultrasound has many uses, and here we will look at SONAR and medical imaging.

Sonar stands for 'sound navigation and ranging'. In it's simplest form, it can be used to calculate the depth of the sea. This is done by emitting an ultrasonic pulse, this bounces off of the sea bed as an echo, and the time taken for it to return is recorded. Using, speed = distance/time it is possible to calculate the distance, take the example below.

Properties of Waves

A Wave


Amplitude is the height of the wave from 0 displacement (normal) to the peak, where the peak is the highest point. The Wavelength is the distance from the start to the second point the wave passes 0. i.e. a complete wave.

Period: if it was a displacement/time graph, the period would be equivalent to wavelength, so period is the time for the wavelength. The frequency is 1 / period and measured in Hz (1Hz = 1wave per second)

The Wave Equation




Transverse


The oscillation/vibration is at right angles to the direction of travel. An example of transverse waves are electromagnetic waves

Longitudinal Wave


The oscillations/vibrations are along the line of travel.
Are mechanical waves because it actually moves particles. E.g. sound waves.

Thursday, March 5, 2009

PESKO

PESTA SUKAN DAN KOKURIKULUM SEKOLAH


TARIKH : 8 MAC 2009
TEMPAT : PADANG UTAMA MAAHAD MUHAMMADI LELAKI

*Di harap kepada semua yang terlibat sila hadirkan diri untuk melancarkan perjalanan program. Kepada mana-mana yang berkenaan sila ambil gambar sebagai simpanan dan juga tantapan pengunjung blog V SYARIAH SCIENCE دمش

KAD PESERTA GERAI

Sunday, March 1, 2009