LIGHT MYSTERY DO THIS! Directic Picture A shows the image of the students on water while Picture B shows a glass with refracted light. How do these phenomena happen? A B Photocredits: Cogasa, delos Angeles & Photocredits: Olmeda, Olavides, & Oloya (2020) Gonzales (2020), Ligao National High Ligao National High School, Ligao City, Albay School, Ligao City, AlbayWAVE-PARTICLE DUALITY In 1905, a German physicist named Albert Einstein developed a novel theory about electromagnetic (EM) radiation which is called the wave-particle duality theory. It explains the behavior of electromagnetic radiation as a wave and a particle. Einstein explained that when an electron returns to a lower energy level and gives off slactromagnatic anorgy, the energy is emitted as a discrete "packet" of energy. This packet of energy is called photon. According to Einstein, a photon is in a form of particle but moves like a wave (see Figure 1). The theory suggests that waves of photons traveling linrough maller or space make up electromagnetic radiation. Energy of a Photon An election returns to a . The proton lower energy leve and travers outwards Photon releases a discrete energy is the energy carried by a photon. The photon energy is directly proportional to its electromagnetic frequency and thus, inversely proportional to the wavelength, the higher amount of photon's frequency, the higher its energy and the longer the wavelength of the photons, the lower its energy. There are different units that can be used in Source: Wave-Faride Theory. https:/flexbooks.ck12.org/cbook/ck-12- photon energy, these are electronvolt (eV) and physics-Texbook-2.0/section:13.4 primary/lessonwave-particle-theory-ms-ps the joule. One joule is equivalent to 6.24 x 1018 eV, the large units can be used for representing the energy of Figure 1. Wave of photon travelling through matter or space photons with higher frequency and higher energy like gamma rays, as contrasting to photons with low energy photons, like those in the radio frequency region of the electromagnetic spectrum. Evidence for the Wave-Particle Theory Evidences were discovered and showed after Einstein proposed his wave- particle duality theory. Scientists shone laser light using two slits in a barrier that blocked the light (see Figure 2). They took photos of the light that passed through the slits using a very sensitive camera. The photos showed small pinpoints of light passing through the double slits. This seemed to reveal that light consists of very small particles. However, when the camera was exposed to the light for a long time, the pinpoints accrued in bands that look like Source: Wave-Particle Theory. https/lexbooks.ck12.org/ebook/ck-12-physics~ interfering waves . Therefore, lexbook-2.0 section/13.4/primary lesson/wave-partide theory-ms-ps the experiment exhibited that light appears to Figure 2. Experiment showing that light is both a particle and consist of particles that act like waves. waveParticle and Wave Refraction When a light beam travels between two media having different refractive indices, the Ight beam undergo refraction, and changes its direction when passes through differele Refraction of Particles and Waves medium (see Figure 3 & 4) just like in picture B which shows that the light was Force Pulls Particles bended when it passes through a glass of into Medium Waves Wave Edge Bends at water. On the other hand, a model for each Particles Entry can be devised to explain and to determine whether the light beam is composed of waves or particles, phenomenon (see Figure 4). Huygens' wave theory explains that a small portion of each angle Wave Edge Bends at wavefront should hit the second medium Exit Opposite Force before the rest of the front reaches the Pulls Particles interface. Light beam will start to move From Medium through the second medium while the other Figure 4. Refraction of Particles and Waves part of the wave is still traveling in the first medium, but will move slower due to the higher refractive index of the second medium. The light beam will bend into the second medium since the wavefront is traveling at two different speeds, therefore changing its angle of propagation. Particle and Wave Reflection Wave theory speculates that a Particles and Waves Reflected by a Mirror source of light releases light waves that spread in various directions. The light waves are reflected according to the arrival angles when the light beam touches a mirror, but with each wave turned back to front that yielded a reversed image (Figure 3). The shape of arriving waves depends upon the distance of the light source from the mirror. Light Particles Waves that came from a close source maintains Figure 5. Particles and Waves Reflected by a Mirror a spherical, highly curved wavefront. On the other hand, the light beam being emitted from a distance source will spread more and impact the mirror with wavefronts that are almost planar. In the case for a particle nature of light, light emitted by a source, regardless of the distance, light arrives at the mirror surface as a stream of particles, which bounce away or are reflected from the smooth surface (see Figure 5). Since the particles are very small, a great number of particles are involved in a propagating light beam. Upon touching the mirror, the particles bounce from various points, so their order in the light beam is reversed upon reflection to produce a reversed image. Both the particle and wave theories explain reflection from a smooth surface. However, the particle thenry also suggests that if light heam touches scattering the light. a very rough surface, its particles bounce away at different angles which resulted to the SOURCE & PHOTOCREDITS: Robert T. Sutter, Matthew J. Parry-Hill and Michael W. Davidson Accessed October 19, 2020. https://micro.magnet.fsu.edu/primer/iava/particleorwave/refraction/index.htmWORD BANK The following terms used in this module are defined as follows: WAVE-PARTICLE DUALITY THEORY OF LIGHT states that light acts as a wave when it moves through space and as a particle when it interacts with matter. . ELECTROMAGENTIC WAVE is an energy-carrying wave emitted by a vibrating charge (often electrons) that is composed of oscillating electric, and magnetic fields that regenerate one another. HUYGEN'S PRINCIPLE states that if the position of a wave front at one instant is known, then the position of the front at a later time can be constructed by imagining the front as a source of secondary wavelets. Huygens's principle can be used to derive the laws of reflection and refraction. INDEX OF REFRACTION OF A MATERIAL is the ratio of the speed of light in vacuum to the speed in the material. If is the wavelength in vacuum, the same wave has a shorter wavelength in a medium with index of refraction n. LAW OF REFLECTION states that the angle of reflection equals the angle of incidence. LAW OF REFRACTION relates the angles of incidence and refraction to the indexes of refraction of the materials. LIGHT is an electromagnetic wave. When emitted or absorbed, it also shows particle properties. It is emitted by accelerated electric charges. PLANE OF INCIDENT is a single plane where all incident, reflected, and refracted rays and the normal lie. REFLECTION is the return of light rays from a surface in such a way that the angle at which a given ray is returned is equal to the angle at which it strikes the surface. When the reflecting surface is irregular, the light is returned in irregular directions; this is diffuse reflection. In general, the bouncing back of a particle or wave that strikes the boundary between two media REFRACTION is the bending of an oblique ray of light when it passes from one transparent medium to another. This is caused by a difference in the speed of light in the transparent media. In general, the change in direction of a wave as it crosses the boundary between two media in which the wave travels at different speeds. WAVEFRONT is a surface of constant phase; wave fronts move with a speed equal to the propagation speed of the wave Hurray! you have completed your learning episodes in this module! Please check your answers by referring to the answer key. Congratulations!APPLY WHAT YOU HAVE LEARNED Directions: Describe and explain the property of light depicted in each photo below. Write your answers on the provided spaces. Photo credits: Oraa, Penafiel & Peralta (2020), Ligao National High School, Ligao City, Albay Photo credits: Oraa, Penafiel & Peralta (2020), Ligao National High School, Ligao City, AlbayDirections: Answer the following questions. Write your ASSESS WHAT YOU answers in your notebook. HAVE LEARNED What is the wave-particle duality of light? 1 . 2. How does light propagated, reflected and refracted? Draw the wave and particle diagram to answer this question. REFLECT Directions: Write your thoughts about the following questions. 1. What are the practical applications of reflection and refraction of light that can be found inside your community? 2. What are the evidences of particle and wave reflection and particle and wave refraction that can be observed in your locality? REINFORCEMENT Directions: Look around inside your house, take a picture exhibiting the materials, phenomena and scenarios where you can observe reflection and refraction of light. Make an inference about how light is being propagated using wave and particle theory