How holograms works?

Though holography is often referred to as 3D photography, this is a misconception. A better analogy is sound recording where the sound field is encoded in such a way that it can later be reproduced. In holography, some of the light scattered from an object or a set of objects falls in the recording medium. A second light beam, known as the reference beam, also illuminates the recording medium, so that interference
occurs between the two beams.

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Types of holograms?

Several types of holograms can be made. Transmission holograms, such as those produced by Leith and Upatnieks, are viewed by shining laser light through them and looking at the reconstructed image from the side of the hologram opposite the source. A later refinement, the “rainbow transmission” hologram allows more convenient illumination by white light rather than by lasers or other monochromatic sources. Rainbow holograms are commonly seen today on credit cards as a security feature and on product packaging.

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What is Holography?

Holography (meaning writing or drawing in Greek) is the science of producing holograms. It is a technique that allows the light scattered from an object to be recorded and later reconstructed so that it appears as if the object is in the same position relative to the recording medium as it was when recorded. The image produced changes as the position and orientation of the viewing system changes in exactly the same way as if the object were still present. Holograms can also be made using other types of waves.

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The Pulse

The easiest way to know the working of the heart is through the pulse. We can find our pulse by lightly pressing on the wrist, just below the thumb. The pulse (beat) is caused by the contraction (squeezing) of the heart.

We can measure the heart rate by counting number of beats we can feel in 1 minute. When we are resting, pulse rate could vary between 70 and 100 beats per minute. When the heart muscle contracts (systole), it pumps blood out of the heart.

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Understanding blood pressure

The force which the blood exerts on the walls of the blood vessels is called blood pressure. As the heart beats, it pumps blood through a system of blood vessels, which carry blood to every part of the body. Diastolic  pressure is the pressure that is exerted on the walls of the various arteries around the body in between heart beats when the heart is relaxed. Systolic pressure measures the amount of pressure that blood exerts on arteries and vessels while the heart is beating.

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Arteries and Veins

Blood moves through many tubes called arteries and veins, which together are called blood vessels. These blood vessels are attached to the heart. The blood vessels that carry blood away from the heart are called arteries. The ones that carry blood back to the heart are called veins.

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What are Valves?

Valves regulate the flow of blood in a singular direction. Each chamber has a sort of one – way valve at its exit that prevents blood from flowing backwards. When each chamber contracts, the valve at its exit opens. When it is finished contracting, the valve closes so that blood does not flow backwards.

There are four valves in the heart as follows:
1. The tricuspid valve
2. The pulmonary valve
3. The mitral valve
4. The aortic valve

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