First of all, I would like to express my appreciation to everyone who had assist me with my Science folio by wishing thank you to my Science Teacher, Pn.Noor Azah for her guidance in explaining how to do my science folio entitled the Limitation of Sight and Hearing.Special thanks are also given my mother, Puan Jamillah for her effort in helping me for my financial or moral support. Without her support and guidance, this portfolio will not be able to meet it success.Lastly,I thanked to my friends for sharing their knowledges with me about the

Especially for science our sense of vision is very limited. Much of the world and the universe is either too far away or too small for us to observe with our naked eyeballs. As we so often do, we overcome our limitation of sight by using appropriate optical devices such as microscope, binocular and others. In 1609 when Galileo capitalized on centuries of experimentation with glass optics by popularizing a practical telescope; he not only provided something that extended the human sense of sight but also opened new worlds for us to discover – the very small and the very far away.

At certain distance from the eye, some object that you can see previously may disappear, after certain moment, it will reappear.This phenomenon occurs because the image of the object has fallen onto the blind spot in your eye.This blind spot does not have any photoreceptors. As result, the image of the cross that falls on this spot cannot be detected, and that's why you can't see it.

Optical illusion are caused by disturbances to the nerve impulses going to the brain.The disturbances may caused by the object or condition around the object.The brain cannot accurately interpret the information sent by the receptors in eye.That’s why you will incorrectly interpret what you actually see.

Sounds are produced by vibrations. Sounds needs a medium to travel. Sound can travel through solids, liquids and gasses. Sound cannot travel through a vacuum. Hard and smooth surfaces like walls are good reflector of sound. Soft and rough surfaces like curtains are good absorbers of sound. Reflected sound are called echo. Humans also have hearing limitation.Without any devices, our hearing was limited. Limitation of hearing can overcome by using appropriate hearing aids such as   stethoscope, megaphone, microphone, headphone and others. The range of frequency of hearing in human is 20 Hz and 20000 Hz. It was different according to the age of a person.

The objectives of learning about the limitation of sight and hearing :- I have learnt that our hearing and sight has its limitation.- I have learnt that we van overcome the limitation of our sight and hearing by using or wearing technology devices.- The technology devices have make our live easier : (i) Doctors use stethoscope to hear our heartbeats.(ii) Teachers use microphone in the assembly. (iii) Scientists use microscope to see the virus.

It use to magnify the objects that very tiny which cannot be seen by our naked eyes such as bacteria , virus , protozoa , fungus and others.

Invented in 1625 by Zacharias Jansson.

Compound microscope : It has at least 2 lenses.In a compound microscope, the lens closer to the eye is called the eyepiece. The lens at the other end is called the objective. It can give a clear magnification by 300 to 2000 times.These types of microscopes are commonly used in schools such as high schools to benefit their students in science classes such as  biology or  chemistry class.

High power microscope : It uses extensively in research .For example is electron microscope.It can reveal the structure of smaller objects such as virus and other tiniest objects because electrons have wavelengths about 100,000 times shorter than visible light photons.It uses electron beams and can magnify an object up to one million times.

Zacharias Jansson

Compound microscope

Electron microscope

It is used too see distant objects from outer space appear as bright and clear such as stars and planets.

Invented 1608 by Hans Lippershey. The first known practical telescopes were invented in the

Netherlands at the beginning of the 17th century by using glass lenses.

An instrumentent that aids in the observation of remote objects by collecting electromagnetic radiation.

Consists of two convex lenses such as objective lens and eyepiece lens.

Reflecting telescope : Reflecting telescope is telescope that use mirrors. It most commonly use a concave main mirror at the bottom of the tube, which focuses light back up to the top of the tube. There, a small flat mirror deflects the light at right angles to an eyepiece on the side of the tube.

Refracting telescope : Refracting telescope is telescope that use lenses to gather and focus light. Refractors deliver sharp, high-contrast images with crisp views of the moon, planets and stars.It is easy to aim.

Hans Lippershey

Reflecting Telescope

Refracting Telescope

It is used to see tiny distant objects such as bird in sky. Invented in 1825 by J.P. Lemiere It is a pair of short telescope. Symmetrical telescope mounted side by side and aligned to

point accurately in the same direction allowing the viewer to use both eyes when viewing distant objects.

J.P. Lemiere

Old Binocular

Latest Binocular

It is an instrument to see a view beyond and obstructing object that used in war and submarine.

Invented by Sir Howard Grubb in 1902 An instrument for observation from a concealed position. Consists of an outer case with mirrors at each end set

parallel to each other at 45 degree angle.  A simple one is made of two mirrors while a complex one

many consist of reflecting prisms and several lenses to give clearer and magnified images.

Sir Howard Grubb

Captain Raymond W. Alexander in control room of a U.S. Navy submarine in World War II in 1942.

Principle of the periscope:a Mirrorsb Prismsc Observer's eye

It is an instrument to examine the tiny objects appear larger than the original.

Invented by Roger Bacon. Convex lens that is used to produce a magnified image of an

object. It also called as a hand lens in a laboratory context.

Roger Bacon

Magnifying Glass

It is use to see the internal organs. Example is to determine the location of a fracture in a bone. It is also use to inspect baggage at the airports. Inverted by Wilhelm Conrad Röntgen a German physicist on 8

November 1895. Types of x-ray machines :

1. CT Scanner2. Bone X-Ray Machine3. Backscatter X-Ray Machine4. Linear Accelerator5. X-Ray Fluorescence

Wilhelm Conrad Rontgen

X – ray machine

It is used to scan and see the condition of the baby in a pregnant mother.

It is invented by Ian Donald in 1957. A cyclic sound pressure wave with frequency greater than

the upper limit of the human hearing range. This is used for obstetrics, for heart and for biopsy

Ultrasonic waves - create images -organ, fetus. Device shaped like microphone is pressed against the area

being scanned. This device sends out very high frequency sound waves

into the area being scanned. The waves bounce back upon hitting an organ and an

image of the organ is then obtained on computer screen.

Ultrasound machine

Ian Donald

It is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal.  Invented by Alexander Graham Bell in 1876.

Microphones are used in many applications such as telephones, tape recorders, karaoke systems, hearing aids,

motion pictureproduction, live and recorded audio engineering, FRS radios, megaphones, in radio and television broadcasting and in computers for recording voice,speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic checking or knock sensors. Most microphones today use electromagnetic induction (dynamic microphone), capacitance change (condenser microphone), piezoelectric generation, or light modulation to produce an electrical voltage signal from mechanical vibration.

Alexander Graham Bell

Microphone

It allows medical professionals to listen to sounds produced by the internal sounds of an animal or human body. Any abnormal function within these systems in the body can be immediately spotted with proper use of a stethoscope.

Invented by Rene Laennec in France. It is often used to listen to heartbeat sounds. It is also used

to listen to intestines and blood flow in arteries and veins. A stethoscope that intensifies auscultatory sounds is called

phonendoscope.

Rene Laennec

Stethoscope

It boosts weak sounds and increases the volume of sound. Invented by Samuel Morland and Athanasius Kicher in 1655. The megaphone also known as loud hailer. The term ‘megaphone’ was first associated with Thomas

Edison’s instrument 200 years later.In 1878,Edison developed that device

The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it, and the sound waves radiate out the wide end.

Samuel Morland and Athanasius Kicher

Megaphone

It collects and amplifies sounds before sending them to the

middle ear.

Invented by Nathaniel Baldwin in 1937.

There are sometimes known as ear speakers or colloquially.

The in – ear versions are also known as earphones or earbuds.

The earphone is very small headphones that are fitted directly

in the outer ear, facing but not inserted in the ear canal.

It is portable and convenient.

Nathanial Baldwin

Earphone

It is an electronic sound amplification and distribution system

with a microphone, amplifier and loudspeakers, used to allow a

person to address a large public.

It amplifies voices so that they can be heard from far away.

Invented by Edwin Jensen and Peter Pridham.

Simple PA systems are often used in small venues such as

school auditoriums, churches, and small bars.

Nathanial Baldwin

Public Address System ( PA System )

Limitation of sight : We cannot see objects that are either too

close to or too far away from our eyes.Objects that are too small or are blocked by other opaque objects are also invisible to us.To overcome our limitations of sight ,we use optical devices such as microscope,binocular and other devices to help us see objects more clearly.

Limitation of hearing: We cannot hear all the sounds around

us.Different people have different limitation of hearig.For example, old people generally cannot hear as well as young people.Our ear drums become less sensitive to sound as we grow older.Our ears cannot hearv sounds of either very high pitch,such as soundsproduced by bats,or very low pitch,such as sounds from low pitched notes of a double bass.To overcome the limitations of hearing,scientists have invented a

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2. http://prezi.com/d4dtuf1twlfe/technology-devices-for-overcoming-

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4. http://simple.wikipedia.org/wiki/Microscope

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