Limitation of Sight and Hearing

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Humans have sight and hearing limitation. Without any devices, our sight and hearing was limited. Most of the limitation of sight can be overcome with the help of certain optical instruments such as magnifying glass, microscope, binoculars and others. The range of frequency of hearing in human 20 Hz to 20 000 Hz. It was different according to the age of a person. Hearing limitations can be overcome by using devices such as microphone, stethoscope, earphone and PA system. All of these devices help us to make our live easier.


The objectives of learning about the limitation of sight :
- I have learnt that our sight and hearing has its limitation.
- I have learnt we can
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•Objective lens and eyepiece magnify image. Types- light microscope, electron microscope

A microscope (from the Ancient Greek: μικρός, mikrós, "small" and σκοπεῖν, skopeîn, "to look" or "see") is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.
There are many types of microscopes, the most common and first to be invented is the optical microscope which uses light to image the sample. Other major types of microscopes are the electron microscope (both the transmission electron microscope and the scanning electron microscope) and the various types of scanning probe microscope.

How to use a microscope
1. When moving your microscope, always carry it with both hands. Grasp the arm with one hand and place the other hand under the base for support.
2. Turn the revolving nosepiece so that the lowest power objective lens is "clicked" into position (This is also the shortest objective lens).
3. Your microscope slide should be prepared with a coverslip or cover glass over the specimen. This will help protect the objective lenses if they touch the slide. Place the microscope slide on the stage and fasten it with the stage clips. You can push down on the back end of the stage clip to open it.
4. Look at the objective lens and the stage from the side and
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