General Physics 2 Quarter 4: Week 3 - Module 3 Total Internal Reflection PDF

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SHSGeneral Physics 2Quarter 4: Week 3 - Module 3Total Internal ReflectionLEARNING TASK:1. EXPLORE on page 112. GAUGE on page 13 - 14General Physics 2 Grade 12 Quarter 4: Week 3 - Module 3: Total Internal Reflection First Edition, 2021Copyright © 2021 La Union Schools Division Region IAll rights rese...

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General Physics 2 Quarter 4: Week 3 - Module 3 Total Internal Reflection LEARNING TASK: 1. EXPLORE on page 11 2. GAUGE on page 13-14

General Physics 2 Grade 12 Quarter 4: Week 3 - Module 3: Total Internal Reflection First Edition, 2021

Copyright © 2021 La Union Schools Division Region I

All rights reserved. No part of this module may be reproduced in any form without written permission from the copyright owners.

Development Team of the Module

Author: MARTIN GREGOR D. ALLADA Editor: SDO La Union, Learning Resource Quality Assurance Team Illustrator: Ernesto F. Ramos Jr., P II

Management Team: Atty. Donato D. Balderas, Jr. Schools Division Superintendent Vivian Luz S. Pagatpatan, Ph.D Assistant Schools Division Superintendent German E. Flora, Ph.D, CID Chief Virgilio C. Boado, Ph.D,EPS in Charge of LRMS Rominel S. Sobremonte, Ed.D, EPS in Charge of Science Michael Jason D. Morales, PDO II Claire P. Toluyen, Librarian II

Target You have learned in the previous modules that electricity and magnetism can be both static. But when they charge or move together they produce a wave known as electromagnetic wave, which is the combination of electric and magnetic fields. In this module, you will learn specific properties of EM wave to include the concept of optics.

After going through this module, you are expected to: 1) relate the properties of EM wave (wavelength, frequency, speed) and the properties of vacuum and optical medium (permittivity, permeability, and index of refraction) (STEM_GP12OPTIVb-12); 2) explain the conditions for total internal reflection (STEM_GP12OPTIVb14); 3) explain the phenomenon of dispersion by relating to Snell’s Law (STEM_GP12OPTIVb-16); and 4) explain polarization of light.

Jumpstart Directions: Read carefully each item. Write only the letter of the best Answer in a separate sheet of paper. ______1. Which light bends most when white light passes through a prism? A. red B. blue C. green D. violet ______2. Which of the following color has the longest wavelength? A. yellow B. red C. blue

D. green

______3. What do you call the bending of light rays as they pass obliquely from one medium to another medium? A. reflection B. refraction C. dispersion D. diffraction ______4. What type of reflection does fiber optic technology rely upon? A. Regular reflection B. Diffuse reflection C. Retroreflection D. Total internal reflection ______5. What will be the arrangement of electromagnetic waves if we will arrange them according to decreasing energy? A. Gamma, radio, microwave B. X-ray, gamma, ultraviolet C. X-ray, light, radio D. Gamma, ultraviolet, X-ray

Discover The Electromagnetic Spectrum

Remember that when a charged particle moves, an electric current is produced. The produced electric current is always surrounded by a magnetic field. If the electric charges move back and forth, the direction of the current will change just as the charge changes its direction. As a consequence, the direction of the magnetic field will also change. According to Faraday’s law, a changing magnetic field generates an electric field. In Maxwell’s work, he made a counterpart to Faraday’s law by stating that an oscillating electric field produces an oscillating magnetic field. The vibrating electric and magnetic fields produce and reproduce each other to generate an electromagnetic wave that emanates from the vibrating charge. Studies have shown that electromagnetic waves are composed of varying frequencies, especially when observed from a vacuum. Hence, electromagnetic waves are presented as an electromagnetic spectrum as shown in the figure on the next page.

Photo credit: en.wikipedia.org

As shown from the figure, the electromagnetic spectrum extends from the longest wavelengths of radio waves up to the high frequencies of gamma rays. This arrangement strengthens the inverse relationships between frequency and wavelength, wavelength and energy, and direct relationship between frequency and energy. Each type of wave occupies a particular range of wavelength known as band. Arranged in increasing frequency, EM waves follow the following order: radio waves, microwaves, infrared, visible light, ultraviolet, Xrays, and gamma rays. Region

Frequency Wavelength Energy (Hz) (m) (J) 9 -1 < 3x10 > 1x10 < 2x10-24

Radio waves Microwaves 3x109 to 3x101 Infrared 3x1011 to 4x1014 4x1014 to Visible 7.5x1014 light Ultraviolet 7.5x1014 to 3x1016 X-ray 3x1016 to 3x1019 Gamma ray > 3x1019

1x10-3 1x10-1 7x10-7 1x10-3 4x10-7 7x10-7 1x10-8 4x10-7 1x10-11 1x10-8 < 1x10-11

to 2x10-24 to 2x10-22 to 2x10-22 to 3x10-19 to 3x10-19 to 5x10-19 to 5x10-19 to 2x10-17 to 2x10-17 to 2x10-14 > 2x10-14

Speed (m/s)

Size scale Mountains

3x108

Bacteria Viruses Atoms Nuclei

Refraction of Light A rock falls at different speeds through different liquids such as water, oil, milk, and syrup. The speed of the falling marble depends on the density and viscosity of the liquid. Light also travels at different speeds through different media such as air, glass, and water. The speed of light depends on the optical density of the medium. The optical density of a material is a property related to the speed of light through it. The greater the optical density of the material, the slower is the speed of light traveling through it. When light crosses over from one medium to another, it changes not only its speed but also its direction. When a light ray enters a glass cube, it bends instead of traveling along its original straight line path. The bending of light as it crosses over from one medium to another is called refraction. The Dutch scientist Willebrand Snell performed several experiments to investigate the refraction of light. His findings can be summed up in a principle known as Snell’s law, which states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant. This ratio or constant, known as the refractive index (n), expressed mathematically as

n = sin i sin r

or

n1θ i= n2θr

where i is the angle of incidence in the first medium and r is the angle of refraction in the second medium; (n1) is the index of refraction of the first medium and (n2) is the index of refraction of the second medium.

Speed and index of refraction of various materials Material Vacuum Air Ice Glass Water Diamond

Speed (m/s) 3x108 3x108 2.29x108 1.97x108

Index of refraction (n) 1.00 1.0003 1.61 1.33 2.42

Total Internal Reflection

Photo credit: https://byjus.com/physics/total-internal-reflection/

Consider the following situation. A ray of light passes from a medium of water to that of air. Light ray will be refracted at the junction separating the two media. Since it passes from a medium of a higher refractive index to that having a lower refractive index, the refracted light ray bends away from the normal. At a specific angle of incidence, the incident ray of light is refracted in such a way that it passes along the surface of the water. This particular angle of incidence is called the critical angle. Here the angle of refraction is 90 degrees. When the angle of incidence is greater than the critical angle, the incident ray is reflected back to the medium. We call this phenomenon total internal reflection.

Conditions of total internal reflection: 1) The light ray moves from a more optically dense medium approaches a less optically dense medium (e.g., water-air). 2) The angle of incidence is greater than the critical angle.

Dispersion of Light

Photo credit: https://www.teachoo.com/10869/3123/Dispersion-oflight-by-prism/category/Concepts/

When light passes through a prism, it breaks up into an array of several different colors called a spectrum. This breaking up and spreading out of the beam of light is called dispersion or chromatic dispersion. Examine closely the light rays going through the prism and you will see how each color refracts by varying degrees. Red light is bent least from the original straight line path of white light while violet light is bent the most. Dispersion occurs in nature through the interaction of sunlight and water droplets. Sunlight goes in and out of the suspended water droplets in the air. They act as prisms and refract sunlight into several different colors. The result is one of the most beautiful sights in nature – a rainbow. Note: Any light that gives a spectrum similar to that of sunlight is often referred to as white light.

Polarization of Light

Photo credit: https://byjus.com/physics/polarization-of-light/

Light is the interaction of electric and magnetic fields travelling through space. The electric and magnetic vibrations of a light wave occur perpendicularly to each other. The electric field moves in one direction and magnetic in another though always perpendicularly. So, we have one plane occupied by an electric field, the magnetic field perpendicular to it, and the direction of travel which is perpendicular to both. These electric and magnetic vibrations can occur in numerous planes. A light wave that is vibrating in more than one plane is known as unpolarized light. The light emitted by the sun, by a lamp or a tube light are all unpolarized light sources. As you can see in the image above, the direction of propagation is constant, but the plane on which the amplitude occurs is changing. The other kind of wave is a polarized wave. Polarized waves are light waves in which the vibrations occur in a single plane. Plane polarized light consists of waves in which the direction of vibration is the same for all waves. In the image above, you can see that a plane polarized light vibrates on only one plane. The process of transforming unpolarized light into the polarized light is known as polarization. The devices like the purple blocks (polaroids) you see are used for the polarization of light. Polarization Applications Following are the applications of polarization: • •

Polarization is used in sunglasses to reduce the glare. Polaroid filters are used in plastic industries for performing stress analysis tests.

Explore Can You Remember? Direction: Answer the questions comprehensively and concise. Use a separate sheet of paper for your answer.

1) State Snell’s law. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ 2) Explain the dispersion of light. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ 3) Which has a greater optical density, water or air? When light crosses over from water to air, does it bend towards or away from the normal? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ 4) Explain the phenomenon called total internal reflection? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ 5) How does polarization reduce glare? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________

Deepen

Performance Tasks

A. Poet/Composer/Artist: Launch an art exhibit that focuses on light. To synchronize the materials, the theme “Life without light” shall be considered in the poems, songs, paintings, or photographs that they will be submitting for the event. B. Biologists: Light can be produced through incandescence and luminescence. Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek word bios which mean “living,” and the Latin word lumen which means “light”. Collect at least ten pictures or video clips of organisms that possess the ability (bioheminescence). During the presentation, discuss the habitat of the organisms, chemicals involved, and the chemical reactions responsible for the bioluminescence. Explain the benefits of this phenomenon to the stated organisms. C. Devise or create an activity about EM wave, total internal reflection, and dispersion of light or polarization of light. Include the following to your report: objective, material, procedure, questions, and conclusion.

Gauge

Directions: Read carefully each item. Write only the letter of the best answer. Use a separate sheet of paper for your answers. A. Multiple Choices Test (5 points) ______1. Which of the following color has the longest wavelength? A. yellow B. red C. blue

D. green

______2. What will be the arrangement of electromagnetic waves if we will arrange them according to decreasing energy? A. Gamma, radio, microwave B. X-ray, gamma, ultraviolet C. X-ray, light, radio D. Gamma, ultraviolet, X-ray ______3. What do you call the bending of light rays as they pass obliquely from one medium to another medium? A. reflection B. refraction C. dispersion D. diffraction ______4. What type of reflection does fiber optic technology rely upon? A. Regular reflection B. Diffuse reflection C. Retro reflection D. Total internal reflection ______5. Which light bends most when white light passes through a prism? A. red B. blue C. green D. violet

B. On the space provided before each number, write A if the first statement is true and the second statement is false; B if the first statement is false and the second statement is true; C if both statements are true; or D if both statements are false. (2 points each number)

______1.

The bouncing of a light ray from a surface is called reflection of light. Refraction of light happens whenever light strikes a mirror.

______2.

The limiting of the planes where light waves propagate is the polarization of light. Polarized glasses counter the glare from metallic surfaces by not allowing light of a particular orientation to pass through.

______3.

Total internal reflection always happens whenever the light rays passes from a medium of optically less dense to a more optically dense medium. Total internal reflection will happen as the light ray goes from inside a diamond to the air outside, but not when the light ray goes from the air to the diamond.

______4.

The critical angle for material C is 570. If an incident ray approaches the boundary between material C and the air at 59 0, the light ray will be bent back and total internal reflection happens. The critical angle for material C is 570. If an incident ray approaches the boundary between material C and the air at 59 0, the refracted ray will lie along the boundary between the material.

______5.

The result of dispersion is the use of fiber optics The result of total internal reflection is the formation of rainbow.

References Books: Aquino, Marites et al. 2012. Science Links-Physics. Sampaloc, Manila. Rex Book Store, Inc. Caintic, Helen E. 2017. General Physics 2. Quezon City. C and E Publishing, Inc. David, Oliver M. et al. 2012. Discover Science: Physics. Makati. Diwa Learning Systems, Inc. Nolasco, Fernando et al. 2010. Integrative Physics. Makati City. Salesiana Books by Don Bosco Press, Inc....