PHYSICAL SCIENCE 2nd QUARTER POINTERS I. ANCIENT GREEK PHYSICS AND ASTRONOMY It was PYTHAGORAS AND HIS PUPILS who were first to propose a spherical Earth In 500 to 430 B.C., ANAXAGORAS further supported Pythagoras' proposal through his observations of the SHADOWS THAT THE EARTH CAST ON THE MOON DURING A LUNAR ECLIPSE Around 340 B.C., ARISTOTLE listed several arguments for a spherical Earth. 1. The NORTH STAR was believed to be at a fixed position in the sky. However, when the Greeks traveled to places nearer the equator, like Egypt, they noticed that the NORTH STAR is closer to the horizon. 2. Aristotle argued that if the MOON AND THE SUN WERE BOTH SPHERICAL, then perhaps, the EARTH WAS ALSO SPHERICAL. 3. If the Earth was flat, then a SHIP TRAVELING AWAY FROM AN OBSERVER SHOULD BECOME SMALLER AND SMALLER UNTIL IT DISAPPEARED. 4. IF YOU STICK A STICK IN THE GROUND, IT WILL PRODUCE A SHADOW. The shadow moves as time passes. If the world had been flat, then two sticks in different locations would produce the same shadow. ISAAC NEWTON first proposed that Earth was not perfectly round. Instead, he suggested it was an OBLATE SPHEROID—a sphere that is squashed at its poles and swollen at the equator. The Universe has 2 Domains: A. CELESTIAL DOMAIN ▪ Naked eye observations that led to the belief that the earth must be round and not flat. ▪ Celestial Bodies move in the celestial sphere in 2 ways: DIURNAL AND ANNUAL MOTION. ▪ DIURNAL MOTION is the apparent daily revolution of the celestial sphere around the celestial poles as a direct effect of the Earth’s rotation on its axis ▪ ANNUAL MOTION is the apparent yearly motion of the stars, including the Sun as seen from the Earth due to the Earth's revolution around the Sun. B. TERRESTRIAL DOMAIN ▪ Objects on earth and their motion are constantly changing. ▪ THREE VIEWS OF MOTION OF ARISTOTLE 1. According to NATURAL MOTION, objects tend to go back to their natural state, which is based on the element that composes them 2. VOLUNTARY MOTION is the motion of humans and animals due to their innate will to move 3. INVOLUNTARY MOTION It is the motion of minerals and plants due to mechanical forces. II. ASTRONOMICAL PHENOMENON OBSERVE BEFORE THE INVENTION OF TELESCOPE CONSTELLATIONS It is possible with unaided eye to observe that there are apparently patterns in the scattering of the stars. From the earliest record history, names have been given to groups of stars because their arrangement suggested animals, gods, and legendary heroes. Even today these star patterns are called CONSTELLATIONS. PHASES OF THE MOON Ancient people have observed that the moon changes its path and its appearance within a period of 29.5 days. They observed that the moon changes its appearance from semicircular disk to full circular disk. These phases of the moon as the BASIS OF ANCIENT CALENDARS. 1. When the MOON IS BETWEEN THE EARTH AND THE SUN, it is NEW MOON 2. A WAXING CRESCENT MOON occurs when the moon begins to become visible again after a New Moon. The face of the moon seen on the earth and a small – lighted side is seen. 3. The FIRST QUARTER MOON occurs when the moon reaches the first quarter of its orbit around the earth. 4. A WAXING GIBBOUS moon means the visibility of the moon is getting bigger. It is bigger than a semicircle but smaller than a full moon. 5. The FULL MOON is visible when the moon is on the opposite side of Earth than the sun. 6. A WANING GIBBOUS moon comes after the Full Moon. 7. The THIRD QUARTER MOON is the opposite view of the First Quarter moon. It looks like half of a moon but remember the moon is a sphere. 8. A WANING CRESCENT moon has less than half of the moon still visible. SOLAR AND LUNAR ECLIPSE a) LUNAR ECLIPSE occurs when THE EARTH CASTS ITS SHADOW ON THE MOON when the Earth is between the Sun and the Moon. A phenomenon such as this is known as a lunar eclipse wherein the moon changes into a dark or blood red color. b) SOLAR ECLIPSE occurs when the MOON IS IN BETWEEN THE SUN AND THE EARTH, and the MOON PARTIALLY OR COMPLETELY BLOCKS OUT THE SUN III. TYCHO BRAHE’S INNOVATION AND EXTENSIVE COLLECTION PAVED THE WAY FOR KEPLER’S LAW TYCHO BRAHE made the most precise observations that had yet been made by devising the best instruments available before the invention of the telescope. He provided ACCURATE MEASUREMENT OF STARS AND PLANETS POSITION KEPLER found that the orbits of the planets followed three laws. 1. Kepler’s first law, LAW OF ELLIPSE: the planets move in an ellipse (a squashed circle) with the Sun at one focus point, offset from the center. 2. Kepler’s 2nd law, LAW OF EQUAL AREAS: A line joining a planet and the Sun sweeps out equal areas during equal intervals of time. 3. Kepler’s 3rd law, LAW OF EQUAL PERIOD: There is a precise mathematical relationship between a planet’s distance from the Sun and the amount of time it takes revolve around the Sun. IV. Aristotelian and GALILEAN VIEWS ON FREE FALL MOTION MOTION Is the movement or change in location of an object over time. It is often described in terms of direction, location, and speed. FREE FALL MOTION is a type of motion wherein no other factors aside from gravity influences the acceleration of an object. IT IS A STRAIGHT-LINE MOTION CAUSED BY THE GRAVITATIONAL PULL OF THE EARTH ARISTOTLE’s THEORY OF MOTION - Classified motion as NATURAL AND VIOLENT - - - 1. He also categorized NATURAL MOTION in terms of direction straight up, straight down, and circular (e.g., motion of celestial bodies). 2. VIOLENT MOTION – an imposed motion either by pulling or pushing. A MOVING OBJECT COMES TO REST BECAUSE IT SEEKS ITS NATURAL STATE OF REST. GALILEAN VIEWS ON MOTION If there are no interference, objects moving in a straight line will continue to move without the need of force. a) DOWNWARD SLOPE – INCREASING SPEED b) UPWARD SLOPE – DECREASING SPEED c) HORIZONTAL PLANE – NO CHANGE IN SPEED In the absence of air resistance (a vacuum) all objects fall at the same velocity. V. NEWTON’S LAW OF MOTION FIRST LAW OF MOTION: LAW OF INERTIA - AN OBJECT AT REST WILL REMAIN AT REST UNLESS ACTED ON BY AN UNBALANCED FORCE. AN OBJECT IN MOTION CONTINUES IN MOTION WITH THE SAME VELOCITY AND IN THE SAME DIRECTION UNLESS ACTED UPON BY AN UNBALANCED FORCE. - INERTIA is an object’s resistance to changes in motion. - AN OBJECT WITH A LARGER MASS HAS A LARGER INERTIA SECOND LAW OF MOTION: LAW OF ACCELERATION - THE ACCELERATION OF AN OBJECT IS DIRECTLY RELATED TO THE NET FORCE AND INVERSELY RELATED TO ITS MASS. ACCELERATION OF AN OBJECT DEPENDS ON TWO THINGS, FORCE AND MASS. THIRD LAW OF MOTION: LAW OF ACTION AND REACTION - FOR EVERY ACTION (FORCE) IN NATURE THERE IS AN EQUAL AND OPPOSITE REACTION VI. PHOTON CONCEPT A PHOTON IS THE SMALLEST DISCRETE AMOUNT OR QUANTUM OF ELECTROMAGNETIC RADIATION. IT IS THE BASIC UNIT OF ALL LIGHT. Basic Properties of Photon 1. Behave like a particle and a wave, simultaneously 2. Move at a constant velocity, c = 3 𝑥 10^8m/s (i.e. "the speed of light"), in empty space 3. Have zero mass and rest energy 4. Carry energy and momentum, which are also related to the frequency (f) and wavelength (λ) of the electromagnetic wave, as expressed by the equation e = hf and p= f/λ. 5. Can be destroyed/created when radiation is absorbed/emitted. 6. Can have particle-like interactions (i.e. collisions) with electrons and other particles, such as in the compton effect in which particles of light collide with atoms, causing the release of electrons. THE AMOUNT OF ENERGY IS DIRECTLY PROPORTIONAL TO THE PHOTON'S ELECTROMAGNETIC FREQUENCY and thus, equivalently, is inversely proportional to the wavelength. The higher the photon's frequency, the higher its energy. Equivalently, the longer the photon's wavelength, the lower its energy. OBJECTS APPEAR IN DIFFERENT COLORS BECAUSE THEY ABSORB SOME COLORS (WAVELENGTHS) AND REFLECTED OR TRANSMIT OTHER COLORS. WHAT WE ARE SEEING WHEN WE SEE AN OBJECT IS REFLECTED LIGHT. WHEN WE SEE AN OBJECT OF A CERTAIN COLOR THAT MEANS THAT LIGHT OF THAT COLOR'S WAVELENGTH IS BEING REFLECTED OFF THE OBJECT. VII. WAVE PROPERTY OF AN ELECTRON In 1900, MAX PLANCK was able to formulate and discover the so called PLANK’S CONSTANT which he included in his discovery of Plank’s radiation law In 1905 German physicist ALBERT EINSTEIN first showed that light, being considered as a form of EM wave, can be thought of as a particle and localized in packets of discrete energy. This was shown in his photoelectric effect experiment. He also FORMULATED THE HYPOTHESIS THAT AN ELECTRON BEING A PARTICLE HAS WAVE-LIKE CHARACTERISTICS. PHOTO ELECTRIC EFFECT - IF A PHOTON HITS AN ATOM OF A CERTAIN MATERIAL, IT MAY BE ABSORBED BY AN ELECTRON OF THAT MATERIAL. - HOWEVER, IF THE PHOTON HAS ENOUGH ENERGY, THE ELECTRON IS EJECTED, OR EMITTED, FROM THE ATOM. The observations of the COMPTON EFFECT in 1922 by American physicist Arthur HOLLY COMPTON could be explained only if the LIGHT HAD A WAVEPARTICLE DUALITY. Fascinated with the idea that light as a wave can have a particle like property, in 1924, French physicist LOUIS DE BROGLIE proposed that ELECTRONS AND OTHER DISCRETE BITS OF MATTER, WHICH UNTIL THEN HAD BEEN CONCEIVED ONLY AS MATERIAL PARTICLES, MUST ALSO HAVE WAVE PROPERTIES SUCH AS WAVELENGTH AND FREQUENCY. Later in 1927, the wave nature of electrons was experimentally established by American physicists CLINTON DAVISSON AND LESTER GERMER on their DAVISSON-GERMER DOUBLE-SLIT EXPERIMENT where an electron was shot in a DOUBLE-SLIT producing an interference pattern on the screen behind the double-slit. An understanding of the COMPLEMENTARY RELATIONSHIP BETWEEN THE WAVE ASPECTS AND THE PARTICLE ASPECTS of the same phenomenon was announced by Danish physicist NIELS BOHR in 1928 The answer to that question was given by German physicist WERNER HEISENBERG in 1927, in his famous HEISENBERG UNCERTAINTY PRINCIPLE. He articulated that both the momentum and position of the electron cannot be measured exactly at the same time. VIII. PROPERTIES OF LIGHT When a beam of white light passes through a medium such as prism, the medium splits the white light into different colors of the spectrum, this is called DISPERSION. Scattering of light is responsible for this BLUE-COLORED SKY, red sky during sunset, dark clouds during rainy days and beautiful horizon. ATMOSPHERIC GASES SCATTER MOST OF THE COLOR WITH THE LEAST WAVELENGTH. The BEAUTIFUL SPECTRUM OF COLORS REFLECTED ON THE SOAP BUBBLES are produced by the INTERFERENCE OF LIGHT. IT OCCURS WHEN 2 WAVES MEET WHILE TRAVELLING ON THE SAME MEDIUM. DIFFRACTION is the slight BENDING OF LIGHT as it passes around the edge of an object. IX. LIGHT PHENOMENA REFLECTION ON A SPOON - - When light rays hit the surface of a CONCAVE MIRROR, SUCH AS THE FRONT OF THE SPOON, which CURVES INWARD, the rays tend to meet or converge at the focal point of the mirror creating a REAL, INVERTED AND SMALLER IMAGE. When light rays strike a CONVEX MIRROR SUCH AS THE BACK OF THE SPOON, which BULGE OUTWARD, the rays tend to scatter or diverge from the focal point. This means the real rays will not meet and create the image but the imaginary one will converge and create the VIRTUAL, UPRIGHT AND LARGER IMAGE MIRAGE - It occurs when light rays are bent causes an object to look displaced due to REFRACTION OF LIGHT AS IT TRAVELS FROM HOT AIR AND COLD AIR. - A mirage is a phenomenon where you think you see water. TYNDALL EFFECT - It is the scattering of light through COLLOID MATERIALS - It can be seen when light particles are scattered by particles in the medium the beam is passing through COLORED FILTERS - A filter can either be a colored glass or cellophane that absorbs certain frequencies of visible light and transmit a particular color frequency that matches the filter’s natural frequency. Light transmission occurs when a transparent allows light to pass through it. SUNLIGHT AND ARTIFICIAL LIGHT - The color of an object that we see depends on the reflected color frequency of visible eyes that reaches our eyes. Different objects absorb and reflect different color frequencies. - Objects reflect certain color frequencies based on the source that illuminates them. Incandescent light bulbs emit lower frequency colors such as red, orange and yellow. Thus, the objects of these colors are enhanced under the incandescent light. - On the other hand, HIGHER FREQUENCY COLORS SUCH AS BLUE, are emitted by FLUORESCENT LIGHT BULBS. This means that a red shirt will appear more red under an incandescent light than in a fluorescent light. In the same way, a blue shirt will appear more blue under a fluorescent light. HALO - Any of a wide range of atmospheric optical phenomena that result when the Sun or Moon shines through thin clouds composed of ice crystals. - IT IS THE COLORED SPOTS OF LIGHT THAT DEVELOPED DUE TO THE REFRACTION OF LIGHT THROUGH ICE CRYSTALS SUNDOGS - Sundogs or parhelion happen due to the refraction of light upon hitting the small crystals that make up cirrus or cirrostratus clouds. These crystals are hexagonal in shape and with faces almost horizontal upon drifting. RAINBOWS - A rainbow is a light phenomenon formed from the combination of several light properties like REFRACTION, REFLECTION AND DISPERSION. Rainbows are usually seen after rainfall because they are formed when light strikes the scattered raindrops in the atmosphere. As shown in the image, light is refracted upon hitting a RAINDROP THAT SERVES AS THE PRISM. - SECONDARY RAINBOW is the result of dispersion, refraction and two reflections from the back surface of the droplet. It is noticeably fainter than the primary rainbow. - SUPERNUMERARY BOWS are faint bow lines that appear just inside the main rainbow. WHITE CLOUDS - Clouds appear white because the water droplets in the clouds scatter all the color frequencies of white light equally DARK RAIN CLOUDS - Rain clouds appear dark because they are too thick that sunlight needs to pass through a lot of water droplets and be absorbed before it can reach the observer’s eye. BLUE SKY - . The atmosphere has an abundance in nitrogen and oxygen particles, which can scatter frequency components of white light. They scatter violet the most, followed by blue and so on. RED SUNSET - In similar way, sunsets appear red because sunlight travels a greater distance as it reaches the horizon and encounters more atmospheric particles, scattering higher frequencies of light until only the red light is left.
