Albert Einstein

Albert Einstein was born on March 14, 1879, in Ulm, Germany. His parents were Hermann Einstein, a salesman and engineer, and Pauline Koch. In 1880, the family moved to Munich, where Einstein's father and his uncle Jakob founded Elektrotechnische Fabrik J. Einstein & Cie, a company that manufactured electrical equipment based on direct current.

The Einsteins were non-observant Ashkenazi Jews, and Albert attended a Catholic elementary school in Munich, from the age of 5, for three years. At the age of 8, he was transferred to the Luitpold Gymnasium, where he received advanced primary and secondary school education until he left the German Empire in 1884.

He was a poor student, and some of his teachers thought he might be retarded (mentally handicapped); he was unable to speak fluently (with ease and grace) at age nine. Still, he was fascinated by the laws of nature, experiencing a deep feeling of wonder when puzzling over the invisible, yet real, force directing the needle of a compass. He began playing the violin at age six and would continue to play throughout his life. At age twelve he discovered geometry (the study of points, lines, and surfaces) and was taken by its clear and certain proofs. Einstein mastered calculus by age sixteen.

In 1894, Hermann and Jakob's company lost a bid to supply the city of Munich with electrical lighting because they lacked the capital to convert their equipment from the direct current (DC) standard to the more efficient alternating current (AC) standard. The loss forced the sale of the Munich factory. In search of business, the Einstein family moved to Italy. When the family moved to Italy, Einstein, then 15, stayed in Munich to finish his studies at the Luitpold Gymnasium. His father intended for him to pursue electrical engineering, but Einstein clashed with authorities and resented the school's regimen and teaching method. He later wrote that the spirit of learning and creative thought was lost in strict rote learning. At the end of December 1894, he travelled to Italy to join his family.

In 1895, at the age of 16, Einstein took the entrance examinations for the Swiss Federal Polytechnic in Zürich. He failed to reach the required standard in the general part of the examination, but obtained exceptional grades in physics and mathematics. On the advice of the principal of the Polytechnic, he attended the Argovian cantonal school (gymnasium) in Aarau, Switzerland, in 1895 and 1896 to complete his secondary schooling. In January 1896, with his father's approval, Einstein renounced his citizenship in the German Kingdom of Württemberg to avoid military service. In September 1896, he passed the Swiss Matura with mostly good grades, including a top grade of 6 in physics and mathematical subjects, on a scale of 1–6. At 17, he enrolled in the four-year mathematics and physics teaching diploma program at the Zürich Polytechnic.

Einstein's future wife, a 20-year old Serbian woman Mileva Marić, also enrolled at the Polytechnic that year. She was the only woman among the six students in the mathematics and physics section of the teaching diploma course. Over the next few years, Einstein and Marić's friendship developed into romance, and they read books together on extra-curricular physics in which Einstein was taking an increasing interest. In 1900, Einstein passed the exams in Maths and Physics and was awarded the Federal Polytechnic teaching diploma.

Though Einstein showed flashes of brilliance during his years at the Zurich Polytechnic, his rebellious personality and penchant for skipping classes saw his professors give him less than glowing recommendations upon his graduation in 1900. The young physicist later spent two years searching for an academic position before settling for a gig at the Swiss patent office in Bern. Though menial, the job turned out to be a perfect fit for Einstein, who found he could breeze through his office duties in a few hours and spend the rest of the day writing and conducting research. In 1905—often called his “miracle year”—the lowly clerk published four revolutionary articles that introduced his famous equation E=mc2 and the theory of special relativity.

By 1908, he was recognized as a leading scientist and was appointed lecturer at the University of Bern. The following year, after giving a lecture on electrodynamics and the relativity principle at the University of Zürich, Alfred Kleiner recommended him to the faculty for a newly created professorship in theoretical physics. Einstein was appointed associate professor in 1909.

Based on calculations Einstein made in 1911, about his new theory of general relativity, light from another star should be bent by the Sun's gravity. Because it was such a bold rewriting of the laws of physics, the theory remained controversial until May 1919, when a total solar eclipse provided the proper conditions to test its claim that a supermassive object—in this case the sun—would cause a measurable curve in the starlight passing by it. Hoping to prove Einstein’s theory once and for all, English astronomer Arthur Eddington journeyed to the coast of West Africa and photographed the eclipse. Upon analyzing the pictures, he confirmed that the sun’s gravity had deflected the light by roughly 1.7 arc-seconds—exactly as predicted by general relativity. The news made Einstein an overnight celebrity. Newspapers hailed him as the heir to Sir Isaac Newton, and he went on to travel the world lecturing on his theories about the cosmos. According to Einstein biographer Walter Isaacson, in the six years after the 1919 eclipse, more than 600 books and articles were written about the theory of relativity.

In 1922, he was awarded the 1921 Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect". While the general theory of relativity was still considered somewhat controversial, the citation also does not treat the cited work as an explanation but merely as a discovery of the law, as the idea of photons was considered outlandish and did not receive universal acceptance until the 1924. Einstein was elected a Foreign Member of the Royal Society (ForMemRS) in 1921. He also received the Copley Medal from the Royal Society in 1925.

Shortly before Hitler rose to power in 1933, Einstein left Berlin for the United States and took a position at the Institute for Advanced Study in Princeton, New Jersey. At the time the Nazis, led by Adolf Hitler, were gaining prominence with violent propaganda and vitriol in an impoverished post-world war I Germany. The party influenced other scientists to label Einstein's work "Jewish physics." Jewish citizens were barred from university work and other official jobs, and Einstein himself was targeted to be killed. Meanwhile, other European scientists also left regions threatened by Germany and immigrated to the U.S., with concern over Nazi strategies to create an atomic weapon.

In the late-1930s, Einstein learned that new research had put German scientists on a path toward creating the atom bomb. The prospect of a doomsday weapon in the hands of the Nazis convinced him to set aside his pacifist principles and team up with Hungarian physicist Leo Szilard, who helped him write a letter urging President Franklin D. Roosevelt to conduct atomic research. Though Einstein never participated directly in the Manhattan Project, he later expressed deep regrets about his minor role in bringing about the Hiroshima and Nagasaki bombings in Japan. “Had I known that the Germans would not succeed in producing an atomic bomb, I never would have lifted a finger,” he told Newsweek. He went on to become an impassioned advocate of nuclear disarmament, controls on weapons testing and unified world government.

Though not traditionally religious, Einstein felt a deep connection to his Jewish heritage and often spoke out against anti-Semitism. He was never a staunch Zionist, but when head of state Chaim Weizmann died in 1952, the Israeli government offered to appoint him as the nation’s second president. The 73-year-old wasted little time in declining the honor. “All my life I have dealt with objective matters,” Einstein wrote in a letter to the Israeli ambassador, “hence I lack both the natural aptitude and the experience to deal properly with people and to exercise official function.”

Einstein died in April 1955 from an abdominal aortic aneurysm. He had requested that his body be cremated, but in a bizarre incident, Princeton pathologist Thomas Harvey removed his famous brain during his autopsy and kept it in the hope of unlocking the secrets of his genius. After winning a reluctant approval from Einstein’s son, Harvey later had the brain cut into pieces and sent to various scientists for research. A handful of studies have been conducted on it since the 1980s, but most have either been dismissed or discredited. Perhaps the most famous came in 1999, when a team from a Canadian university published a controversial paper claiming Einstein possessed unusual folds on his parietal lobe, a part of the brain associated with mathematical and spatial ability.

In the Time's article of 1999, Albert Einstein was chosen as the Person of the Century, on the grounds that he was the preeminent scientist in a century dominated by science. The editors of Time believed the 20th century "will be remembered foremost for its science and technology", and Einstein "serves as a symbol of all the scientists”.

Topic 39 - Photoelectric effect

What is photoelectric effects?
It is the phenomenon of emission of electrons from the surface of metals when they are irradiated with electromagnetic radiation of sufficient frequency and suitable wavelength.

The emitted electrons are called photo electrons and the current so produced is called as the Photoelectric Current.The intensities of photo electrons vary with material.

In the setup below, when ultraviolet is allowed to fall metal plate P, the galvanometer shows deflection.The galvanometer does not deflect when the radiations are blocked from reaching the metal plate.

The electrons are dislodged from the metal surface when they absorbed ultraviolet radiation energy. The galvanometer deflects because of flow of current caused by attraction of electrons by plate C. The stream of electrons complete the circuit.

In the set up below, mercury lamp, zinc plate and both negatively and positively charged electroscope are used.

Causes divergence of the leaf in the uncharged electroscope. Radiations have no effects on the positively charge electroscope. Divergence of the negatively charged electroscope decreases.

For uncharged electroscope, photoelectrons leaves the plate with the net positive charge as they move away from the plate. Positive charges are repelled to the leaf and the plate causing divergence in the leaf.
Radiations have no effect on the positively charged electroscope since the photoelectrons are attracted back by positive charge hence no loss in electrons.
There leaf falls /decrease in divergence for negatively charged electroscope because of loss of charges. This because photoelectrons emitted are repelled by negative charges on the electroscope hence net loss of charge from the electroscope.

Work function (Wo )
Work function is the mminimum energy needed to disloge an electron from a metal surface.This energy is measured in electronvolt (eV) or Joules(J).

Work function can be expressed as

Where
 h = Planck's constant
fo = Threshold frequency.
Photoelectric effect will occur if the energy of incident radiation is greater than the work function.
Threshold frequency(f0 ) is defined as the minimum frequency of incident light required for the photoelectric emission to occur.
Threshold wavelength (λo ) is the maximum wavelength of radiations beyond which no photoemission will occur.
Quantum(quanta) is the small packets of energy propagated. Plural quanta.
Photon is the discrete amount of energy. This energy is given by:
                                               E = hf
Where h is the Planck's constant and f is the frequency of radiations.

Einstein's equation of photoelectric effect
Part of energy from incident radiation is used to dislodge an electron from a metal surface and the rest gives the electron kinetic energy.
                   Energy = (work function) + (maximum KE by the electron)
This can be expressed as.

Since work function (wo) = hfo

This equation is known as Einstein’s equation of photoelectric effect.

Some of the factors affecting photoelectric effect are:
a)Intensity of incident radiation.
b)Applied potential difference between plates.
c)Energy of the radiations.
d)The type of the metal.
For a given metal if the frequency and applied voltage are kept constant; increase in intensity increases photoelectric current. This means that the rate of emission of photoelectrons is directly proportional to the intensity of incident radiations.
Stopping potential is the potential difference applied to stop the electrons from being ejected from the surface when the light falls on it. A graph of stopping potential against frequency is as shown below.

The graph of Vs against f is straight line cutting the x – axis at fo.
The slope of this graph is h/e
The Vs intercept is -wo/e
From this graph both plank’s constant h and the work function Wo can be calculated.

Some of the applications include:
a)Photoemissive cells.
b)Photoconductive cells.
c)Photovoltaic cells.

Photoemissive cells

A retirement message from sister Lydia

Have I been really here for 17 years? That sounds like a long time. Since the year 2002, I have been privileged to have had in my classroom, many fine young boys. 17 years ago, at St. Paul’s Gekano boys high school, some of the learners began to teach me how to teach. They helped me build the first bridges. From them I learned that true teaching is a special partnership. It only really works when the teacher reaches beyond the outer image, looks into the heart, understands and respects what they see. The students’ role is to allow themselves to be seen, not just for who they are, or have been, but also for what they could be.

I look back with gratitude. I entered a profession dedicated to assisting young people achieve their potential, to revealing or finding their best selves. As I leave it, I am taking many of you with me. You will live in my memories. I will always remember the things we achieved together.

I have been asked what I’m going to do now. I am going to do lot of things and very few of them conform to the nation of retirement as a time of waiting for the inevitable end. I am going to travel to places visiting other Christians, consoling the sick, the faint-hearted and the less fortunate in the society. Basically, I will continue doing God’s work here on earth.

I would wish to pay tribute to my colleagues for their support, friendship and exemplars of what it is to serve faithfully and with humility. I will always remember our shared laughter, our joys as well as our struggles.

And lastly, to the dear parents of this young learners, the teachers of this great school that we love so much and our dear young boys, I leave you with this thought. We are unique. We are neither better nor less than anybody else but rather the best or the least of ourselves. I am still working on finding the best of me. Thank-you for being my travelling companions along a large and important part of my way. I am forever grateful for your stimulating company and enormous collection of shared experiences indelibly printed on my mind.

	Thank-you. Happy holidays