PHYSICAL SCIENCE 4th Qtr Week 2: Inertia ans Waves

 

WEEK 2: INERTIA AND WAVES
Name:	◯ HE- A	◯ HE- B	◯ EIM

BEGIN

TOPIC	EXAMPLES/APPLICATIONS/EXPLANATIONS
HOW GALILEO VIEWS INERTIA.	HOW NEWTON EXPLAINS INERTIA
Galileo’s idea is nearly the same as Newton in the stationary state. However, he did not attribute this to zero net force but on the object’s inertia. Figure 13 Galileo's explanation of the Law of Inertia Galileo noted that objects rolled downhill goes uphill with the same level it was released on. If one releases it on a flat plane with no uphill, the object will forever seek its uphill height.	The First Law of Motion, the Law of Inertia states that a body can only be in two states of motion when ZERO net force acts on it. 1)    A body is stationary or not changing position with respect to the observer 2)    A body is moving continuously at constant speed in one direction.   An example of this is when an object on moving cart at constant speed suddenly stops. The object on top continues its motion until another NON-ZERO net force stops it. Figure 14 Newton assumes that bodies can move without force as long as inertia is available.
HUYGEN’s WAVE THEORY OF LIGHT	NEWTON’s CORPUSCULAR THEORY OF LIGHT
During Newton’s lifetime, however, another theory of light was forwarded. In 1678, the Dutch physicist and astronomer Christian Huygens (1629–1695) showed that a wave theory of light could also explain the laws of reflection and refraction.	Until the beginning of the 19th century, scientists view light as a stream of particles emitted by a source that stimulated the sense of sight on entering the eye. Newton’s corpuscular theory, gave simple explanations of some known observations on the nature of light such as reflection and refraction.
Reflection as explained by Wave Theory –waves (as in waves in a basin or pond) bend their “wave fronts” as they encounter a barrier (like the side of a container) Reflected Wave (dashed red) Incident Wave (blue) Figure 15 Reflection is when a wave reflects from a barrier, producing that distinctive reflected wave.	Reflection as explained by Corpuscular Theory – just like a Ping-Pong ball bounces of a surface, light corpuscles* (or little bodies) bounce off surface unaffected by gravity or friction. Incident Path (black arrow) Reflected Path  (dashed line) Figure 16 Reflection is just a particle bouncing off a surface
Refraction as explained by Wave Theory – incident waves slow down as it enters a denser medium by bending towards the point of entry.   Figure 17 Huygens’s refraction predicts that waves bend as they slow down when entering a denser medium.	Refraction by Corpuscular Theory –a light corpuscle enters a denser medium it speeds up, with the particle’s path bending towards the point of entry. Figure 18 Refraction in corpuscular theory requires that the light particles must move FASTER as it enters a denser medium
HUYGEN’s WAVE THEORY OF LIGHT	NEWTON’s CORPUSCULAR THEORY OF LIGHT
Interference as explained by wave theory – This phenomenon happens when light waves passing to double slit (narrow vertical hole) produce alternating bright and dark patterns. ·         This phenomenon, called “The double-slit experiment was performed in 1801 by Thomas Young,” This made light is a wave as a better theory, for 100 years. Figure 19 Huygens’ theory predicts a band of alternating bright and dark is easily explained if light is viewed as wave	Interference as explained by corpuscular theory:   ·         Corpuscular theory has no explanation as why light produces alternating bands of light and dark as it passes through a double slit. The theory expects two bright spots or bright holes with the shape of the slit. Figure 20 Newton's theory predicts two bright spots
MAXWELL’s WAVE THEORY OF LIGHT	EINSTEIN’s PHOTON THEORY OF LIGHT
The wave theory of light strengthened when James Clerk Maxwell used the concept of waves to explain the origin of electromagnetic waves as coming from vibrating electric charges. It also happens that light is an electromagnetic wave, coming from vibrating electrons in an atom. Example: when an electron in an atom vibrates due to energy, they emit light as wave, a way of expelling excess energy received.	Another theory of light emerges as the electromagnetic theory of light cannot explain why experiments show that light energy corresponds to the frequency (color) of light wave rather than light intensity (brightness). Max Planck and later Albert Einstein then explained that light is more like a packet of energy (a quantum, a “particle”) rather than wave.
Figure 21 A vibrating charge releases waves with the same wavelength as its vibrational displacement	Figure 22 Electrons eject photons with the same wavelength as the distance of energy "jump"
WAVE THEORY-WHAT DOES IT EXPLAIN?	PHOTON THEORY-WHAT DOES IT EXPLAIN?
This theory explains that light energy depends on the brightness of light, §  meaning a brighter light, no matter what color has more energy than a dimmer light of any color. §  This theory can’t explain “why a bright red light cannot expose photographic films and a dim blue light can expose photographic films?”. §  Ultraviolet for example can burn human skin (sun burn) since this light has higher frequency than violet or blue light.	This theory called the quantum theory of light explains that energy of light depends on the color of light. This is also called the photon theory of light. §  It is later found out that light energy is varies directly to the frequency (and therefore color) of light. §  It means that blue light has more energy than green light and green light has more energy than red light. §  Higher energy of light when its color is near blue or at blue, and lower energy when its color is near red or at red.
CURRENT THEORY: LIGHT behaves either as a WAVE or as a QUANTUM (PARTICLE)
The success of electromagnetic theory made the modern world of communications possible, from Radio-communications, TV and multimedia, the internet, or any wireless communications, telecommunications became possible. Light is undeniably a wave.	The success of quantum theory in expanding the field of chemistry, solid-state physics, high energy physics and astrophysics is undeniably a proof that light also behaves like a particle. The energy and momentum of each particle is expressed by the Planck’s equation: Energy: E = hf or hc/λ Momentum: hf/c or h/ λ
LIGHT IS A WAVE	LIGHT IS A PARTICLE (A PHOTON)
Conclusion: Light behaves like a wave when situation requires it to behave as a wave, otherwise on specific energy-based situation, light is a photon, a particle of light. Situations like: ·         Refraction - light waves changes speed as it enters another medium and bends as ·         Diffraction – light waves bend around corners but can only be observed on small scale due to the size of the light wave itself. Light wavelength varies from 770 nanometers to 480 nanometers. This size is not easily observed by the naked eyes. Figure 25 Diffraction of light ·         Interference of light: two light sources or double slit experiment shows that light cause alternating bands of light. This is observable in nature. ·         Light Polarization: Light waves can be filtered according to the orientation of the filter. This cannot be explained if light is a stream of particles.	Conclusion: Light behaves like a particle/photon on situations that require light to have high frequencies (and therefore high energy) and low intensity, giving the photons a chance to exhibit its particle like properties. Experiments like: ·         Blackbody Radiation: Best explained by photon theory. The way energy is emitted by light varies as a series of energy levels, not a continuous band of energy. ·         Photoelectric Effect: Photon theory expects that a photon of higher frequency can eject electrons from certain types of metals. ·         X-Ray discovery: The production of x-rays requires that electron energy corresponds to photon energy of light. ·         Compton Effect: This experiment discovered that light has momentum. Momentum is a property of particles. ·         Phosphorescence and Iridescence are light producing phenomena of materials and some living things that is best explained if light is slowly emitted as photons (or quanta) of energy.

                                                                     

THERE IS SUCH THING AS MATTER WAVE (matter that behaves like waves)
·         The duality of behavior of electromagnetic waves led one scientist, Louis de Broglie to speculate that if energy possesses dual characteristics, will matter behave with dual characteristics as well? ·         In his doctorate dissertation, de Broglie predicted that matter can behave as waves, by assigning a wavelength to objects with momentum. λ = h mv ·         Matter wavelength is inversely related to its momentum.
ELECTRON BEHAVES LIKE A WAVE	ELECTRON IS A PARTICLE
Dual slit experiment proves that although electron is a particle, it behaves like a wave when taken as a group of electrons, with no intervention. This experiment shows that matter can behave like a wave. Figure 26 Double slit experiment shows that a stream of electrons will deposit on areas predicted if electron behaves like wave.	Electron will behave like a particle when a detector interferes with its motion, determining them individually as a particle, it then behaves as expected, that is as a particle.  Figure 27 Double slit experiment with an electron detector forces the electrons to behave like a particle.
ELECTRON HAS WAVE PROPERTIES	ELECTRON IS STILL A PARTICLE
Figure 28 Setup Davisson-Germer experiment. Tungsten filament induces a stream of electrons with similar kinetic energy. A movable electron detector detects scattered electrons as they collide the nickel metal.	Figure 29 Result of the experiment shows that a certain speed of electron, it diffracts at a favored angle, which corresponds to an angle if it were a wave, since particles are randomly scattered.

 

WEEK 2: ASSESSMENT
Name:	◯ HE- A	◯ HE- B	◯ EIM
1.      Why is Newton’s explanation more believable than Galileo’s idea of inertia? 2.      Wave theory of light works well in explaining all properties of waves – reflection, refraction, diffraction and interference but cannot explain the concept of energy of light as colors. Does the amount of energy have something to do with it? Explain why or why not. 3.      Looking at red light can cause more eye strain than looking at blue light yet blue is dangerous to the eyes of infants. How do you recommend changes to the tradition of using BLUE clothes for boys and RED clothes for girls?

END.