I bet most of you might know about a water/lawn sprinkler. For those who do not know, a water sprinkler is used to spray water in the lawns and/or used by farmers to irrigate the crop fields.
Image: A water sprinkler
The working principle of water sprinklers
Let us first start with a fun and an interesting science project in order to understand the mechanism by which water is sprayed throgh a sprinkler. For this we need the following materials:
a) A plastic straw
b) A wooden skewer
c) A masking tape, and
d) A container filled with water
The sprinkler will look something as shown below
The detailed steps of the project can be found at the following website links:
The simple principle behind the working of water sprinkler above is that as we spin the straw it forces the water inside to spin. As the spinning continues, any object on it appears to feel a centrifugal force pushing it outward. When we move up the the straw, the water in the straw moves outwards and is pumped upwards. If you spin the straw fast enough then water will exit the straw and fly outwards. Many pumps use the same principle, they consist of a fluid inlet in the middle, and then an impeller spins the fluid, and centrifugal force pushes the fluid outwards and out through an outlet.
The materials used in sprinkler are usually different from the above project. The best selling models of water sprinklers are made from very inexpensive materials as aluminum tubing, plastic, and rubber.
Similar to the brain which controls and send signals for performing various tasks and regulates the actions in most living beings the Operating system takes care of managing the hardware and software running in our laptops, mobiles, microwaves, digital thermometer and most most other modern day electronic devices which have some any sort of event based functions and/or digital displays. This comparison of OS with the brain is only to stress upon its importance as the brains are a lot more complex systems and still being researched upon.
When you are playing a game on your mobile, watching a movie in Netflix on your television or simply running on a treadmill with digital display there are operating systems which tells these devices/machines what to do by controlling the system resources like processors, memory, camera, displays etc. The main function of any operating system is to manage the hardware and software of the device.
Some everyday devices which have their work on an Operating system
|Micro-controller/ Microprocessors||Mobile OS||Computer OS|
|Description||Microprocessors are usually computers on a single integrated circuit.
Micro-controllers usually contains microprocessors and have additional RAM, ROM and other peripherals all embedded on a single chip
|A mobile OS is specifically designed to run on mobile devices such as mobile phones, smartphones, PDAs, tablet computers and other handheld devices. Android, iOS and Symbian OS etc. are some popular ones.
The mobile OS provide platform on top of which other programs and apps can run on mobile devices.
|Computer OS usually comes with any desktop/laptop that you buy. The three most common operating systems for personal computers are Microsoft Windows, Mac OS X, and Linux.
These operating system sits between applications and hardware, managing how applications access hardware and software resources.
|Devices||Digital Thermometer, The ABS or temperature control on your car, the sensor on your security cameras||Mobile phones, handheld scanners, handheld payment processors, iPad, tablets||Laptop, desktop, application and database servers|
To see how an OS differs from another the best thing in my opinion is to use a Raspberry Pi and install the various suggested OS and try them out this summer. Let us know if you need any help or have query regarding running an OS on your Pi.
A compound microscope is an optical instrument with more than one lens and its own light source. Compound microscope is used to obtain high magnification. It is an extension of the magnifying glass which are used to see very small things. The magnifying power of a simple lens is very limited. It is difficult to get a magnification better than a few times without using a highly curved lens with a high refractive index. This kind of lens will have a lot of aberrations that one can not see the image clearly. Therefore, we used two or more lenses which builds up the compound microscope.
Principle of compound microscope
A compound microscope works on the principle that when a tiny object to be magnified is placed just beyond the focus of its objective lens, a virtual, inverted and highly magnified image of the object is formed at the least distance of distinct vision from the eye held close to the eye piece.
Construction of compound microscope
A compound microscope consists of two convex lenses: an objective lens O of small aperture and an eye piece E of large aperture. The lens which is placed towards the object is called objective lens, while the lens which is towards our eye is called eye piece. These two convex lenses i.e. the objective and the eye piece have short focal length and are fitted at the free ends of two sliding tubes at a suitable distance from each other. Although the focal length of both the objective lens and eye piece is short, but the focal length of the objective lens O is a little shorter than that of the eye piece E.
The reason for using the eye piece of large focal length and large aperture in a compound microscope is, so that it may receive more light rays from the object to be magnified and form a bright image.
There are two main parts of compound microscope:
Working of a compound microscope
The ray diagram to show the working of compound microscope is shown in figure. A tiny object AB to be magnified is placed in front of the objective lens just beyond its principal focus fo’. In this case, the objective lens O of the compound microscope forms a real, inverted and enlarged image A’B’ of the object.
Now A’B’ acts as an object for the eye piece E, whose position is adjusted so that A’B’ lies between optical centre C2 and the focus fe’ of eye piece. Now the eye piece forms a final virtual, inverted and highly magnified image A”B”. this final image A”B” is seen by our eye hold close to eye piece, after adjusting the final image A”B” at the least distance of distinct vision of 25 cm from the eye.
Are there any differences between simple microscope and compound microscope? Can you tell them?
Some popular microscopes below $100 are:
|Compound Microscope||AmScope Microscope||Beginner Microscope|
A microscope is an instrument used to produce enlarged images of small objects. The most common kind of microscope is an optical microscope, which uses lenses to form images from visible light. The optical microscope has been a standard tool in life science as well as material science for more than one and a half centuries now. The optical microscopes are of two main types:
a) Simple Microscope b) Compound Microscope
Figure 1. Parts of a simple microscope
The simple microscope is generally considered to be the first microscope. It was created in the 17th century by Antony van Leeuwenhoek, who combined a convex lens with a holder for specimens, magnifying between 200 and 300 times.
The structure of a simple microscope is very simple. It has a body, a stage made of thick glass for placing slides, two clips to fix the slides, a handle, an eyepiece placed with the handle and a mirror. There is an adjustment knob by which the eye piece may be moved upward and downward. The entire body stands on the base or foot.
How to handle the simple microscope?
At first the slide is to fix on the stage with the help of clips. The light should be focused on the slide by moving the mirror. Then keeping the eye in the eye piece the adjustment knob should move in such a way that the eyepiece comes to a position from where the object on the stage can be seen most clearly. At this position, keeping the eye in the eyepiece, the specimen is to be observed carefully, or if required be dissected with the help of forceps or needle whichever is convenient.
Principle: A simple microscope works on the principle that when a tiny object is placed within its focus, a virtual, erect and magnified image of the object is formed at the least distance of distinct vision from the eye held close to the lens.
Figure 2. Working of a simple microscope When an object is placed between the principle focus and the optical centre of a convex lens a virtual, erect and magnified image is formed. The ray diagram is given here explains how an object looks enlarged when viewed through a bi-convex lens. Observe that the object and the image are on the same side of the lens. Image is formed at the least distance of distinct vision from the eye i.e., the distance from the object is approximately equals to 25 cm.
Magnification of Simple Microscope
The magnifying power of a simple microscope is given by:
m = 1 + D/f
D = least distance of distinct vision
F = focal length of the convex lens
The focal length of the convex lens should be small because smaller the focal length of the lens, greater will be its magnifying power. Also, the maximum magnification of a simple microscope is about 10, which means that the object will appear 10 times larger by using the simple microscope of maximum magnification.
Limitations of using a light microscope: Visible light restricts the amount of resolution achieved with a light microscope. Magnification may range from 500x to 1500x. In general, light microscopes require specimens to be thin, small and transparent for optimum viewing. The diffraction limits the resolution to approximately 0.2 µm.
Uses of a simple microscope:
2. A light microscope is also referred to as a?
a) Electron microscope
b) Compound microscope
c) Scanning problem microscope
3. On the microscope stage, what is used to hold the glass slide in place and prevent it from moving?
a) Stage clip
c) Fine adjustment knob
4. Ocular lens
a) Is used to regulate the amount of light on the specimen
b) You look through to see the specimen
c) Projects light upwards through the diaphragm, the specimen, and the lenses
5. What happens when light passes through a condenser lens?
6. What does the objective lens do?
7. What is the maximum magnification of a light microscope?
8. What is the maximum resolution of a light microscope?
9. What are the advantages of a light microscope?