Photoelectric Effect – Particle Nature of Light

Modern physics fully accepts the concept of wave-particle duality in case of light and other electromagnetic radiation. The phenomena such as interference, diffraction, and polarization can only be explained when light is treated as a wave whereas the phenomena such as the photoelectric effect, line spectra, and the production and scattering of x rays demonstrate the particle nature of light. In this article, in order to show the particle nature of light, I have discussed the photoelectric effect along with the necessary equations.


The photoelectric effect is defined as a phenomenon in which the emission of electrons occurs when a beam of light strikes a metal or a cathode surface. For the emission of electrons to take place, the frequency of incident light is required to be greater than a certain minimum value. This value is known as the threshold frequency. The threshold frequency depends on the metal or material of the cathode. For most of the metals, threshold frequency is in the ultraviolet range (wavelengths between 200 nm to 300 nm). If the intensity of light (I) is increased while keeping the frequency same, more electrons are emitted per unit time. Thus, photocurrent is directly proportional to the intensity of light.


The photoelectric effect was correctly explained by the world-famous physicist, Albert Einstein, in the year 1905. It is interesting to know that Einstein was awarded the Nobel Prize in Physics 1921 for his work on photoelectric effect. Einstein figured out that a beam of light comprises of small packages of energy known as photons or quanta. The energy of a photon (E) is equal to the product of the Planck’s constant (h) and the frequency of a photon (f). Frequency (f) of photon = speed of light (c)/wavelength of photon (λ).


The energy of a photon is given by –


E = hf = hc/λ


Planck’s constant (h) = 6.6260755(40) x 10-34

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Along the Rivers – The Gallery Forests

Along the Rivers – The Gallery Forests

In this research paper, I have explored the gallery forests by clarifying the concept behind the term “gallery forest”, and studying their biogeography by reviewing some important ecoregions of North America and South America. I have discussed some of the notable gallery forests found in the Americas with respect to their geography, flora, and fauna. It is hoped that this paper will serve the interests of biologists, ecologists, botanists, zoologists, arborists, forest ecologists, biogeologists, biogeographists, and all other people including professionals, students, and laymen eager to learn about the gallery forests.


A gallery forest is a narrow stretch or strip of forest along the banks of a water body, such as a river or stream, flowing through an otherwise open country. In the above context, an open country is defined as a region that is treeless or sparsely covered with trees. A gallery forest is also known as a fringing forest or riparian forest or riverine forest. Such forests are commonly found along the water bodies flowing through the savanna (or savannah) regions. The gallery forests are known to contain different types of woody vegetation. The width of a gallery forest may vary from several miles to complete absence along the same river.
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A Glance into the Human Brain

A Glance into the Human Brain – Structure and Functions of the Human Brain (Human Brain’s Anatomy and Physiology) – A Voyage Into the Human Brain!

This article describes the structure of human brain (anatomy of human brain) and functions of human brain (physiology of human brain), which is the most complex and mysterious organ of the human body. This article is expected to cater the needs of a variety of audiences including the students, teachers, healthcare professionals, and the laymen. The article has been written in an easy-to-understand language and richly annotated with definitions of difficult medical terms including etymologies.
   

The human brain is the most sophisticated organ of the human body, and can aptly be called as a biological marvel. The brain and the spinal cord constitute the central nervous system (CNS). The brain plays the role of the control tower or control center of the human body, and relies on a vast network of nerves (bundles of fibers of nervous tissue carrying impulses) spread throughout the body. Nerves can be compared to the electrical wiring as they carry electrical impulses.

Noteworthy Facts about the Human Brain!

  • The brain of human beings resembles a small cauliflower in its size and appearance.
  • Human brain is comprised of about 100 billion neurons or nerve cells.
  • The weight of an adult human brain is about 1300 g (about 3 pounds), whereas the weight of a newborn’s brain lies in the range of 350 – 400 g.
  • Although the brain of a human being accounts for only 2 % of the total body weight, it utilizes 20 % of the of the resting total body oxygen consumption.
  • Human brain contains 77 to 78 % water, 10 to 12 % lipids, 8 % proteins, 2 % soluble organic substances, 1 % carbohydrates, and 1 % inorganic salts.
  • The cerebral cortex forms 77% by volume of the human brain.
  • Cerebrum is the largest part of the human brain, whereas Cerebellum is the second largest.
  • Left side of the brain (left cerebral hemisphere) controls the right side of the body, whereas the right side of the brain (right cerebral hemisphere) controls the left side of the human body.

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