Lesson Plan Wao

LESSON PLAN I.

Topic: Electromagnetic Waves

II.

Objectives At the end of the activity, the students should be able to:  compare the relative wavelengths of different forms of electromagnetic waves;  cite examples that show practical applications of the different regions of electromagnetic waves; and  explain the effect of electromagnetic radiation to living things and the environment;

III.

Materials  Worksheet  Chalk/White board marker

IV.

Content A. Electromagnetic Waves Electromagnetic waves are waves which can travel through the vacuum of outer space. Mechanical waves, unlike electromagnetic waves, require the presence of a material medium in order to transport their energy from one location to another. Sound waves are examples of mechanical waves while light waves are examples of electromagnetic waves. Electromagnetic waves are created by the vibration of an electric charge. This vibration creates a wave which has both an electric and a magnetic component. An electromagnetic wave transports its energy through a vacuum at a speed of 3.00 x 108 m/s (a speed value commonly represented by the symbol c). The propagation of an electromagnetic wave through a material medium occurs at a net speed which is less than 3.00 x 108 m/s. This is depicted in the animation below. The mechanism of energy transport through a medium involves the absorption and reemission of the wave energy by the atoms of the material. When an electromagnetic wave impinges upon the atoms of a material, the energy of that wave is absorbed. The absorption of energy causes the electrons within the atoms to undergo vibrations. After a short period of vibrational motion, the vibrating electrons create a new electromagnetic wave with the same frequency as the first electromagnetic wave. While these vibrations occur for only a very short time, they delay the motion of the wave through the medium. Once the energy of the electromagnetic wave is reemitted

by an atom, it travels through a small region of space between atoms. Once it reaches the next atom, the electromagnetic wave is absorbed, transformed into electron vibrations and then reemitted as an electromagnetic wave. While the electromagnetic wave will travel at a speed of c (3 x 108m/s) through the vacuum of interatomic space, the absorption and reemission process causes the net speed of the electromagnetic wave to be less than c. B. Regions of Electromagnetic Waves The types of electromagnetic radiation are broadly classified into the following classes: 1. 2. 3. 4. 5. 6. 7.

Gamma radiation X-ray radiation Ultraviolet radiation Visible radiation Infrared radiation Microwave radiation Radio waves

This classification goes in the increasing order of wavelength, which is characteristic of the type of radiation. While, in general, the classification scheme is accurate, in reality there is often some overlap between neighboring types of electromagnetic energy. For example, SLF radio waves at 60 Hz may be received and studied by astronomers, or may be ducted along wires as electric power, although the latter is, in the strict sense, not electromagnetic radiation at all. The convention that EM radiation that is known to come from the nucleus, is always called "gamma ray" radiation is the only convention that is universally respected, however. Many astronomical gamma ray sources (such as gamma ray bursts) are known to be too energetic (in both intensity and wavelength) to be of nuclear origin. Quite often, in high energy physics and in medical radiotherapy, very high energy EMR (in the >10 MeV region) which is of higher energy than any nuclear gamma ray, is not referred to as either X-ray or gamma-ray, but instead by the generic term of "high energy photons." The region of the spectrum in which a particular observed electromagnetic radiation falls, is reference frame-dependent (due to the Doppler shift for light), so EM radiation that one observer would say is in one region of the spectrum could appear to an observer moving at a substantial fraction of the speed of light with respect to the first to be in another part of the spectrum. For example, consider the cosmic microwave background. It was produced, when matter and radiation decoupled, by the de-excitation of hydrogen atoms to the ground state. These photons were from Lyman series transitions, putting them in the ultraviolet (UV) part of the electromagnetic spectrum. Now this radiation has undergone enough

cosmological red shift to put it into the microwave region of the spectrum for observers moving slowly (compared to the speed of light) with respect to the cosmos.

C. Applications of Electromagnetic Waves Electromagnetic waves have various application in our lives and we don’t even notice that it is an application of it. These applications vary on every region of the electromagnetic spectrum. Radio waves, with the longest wavelength, are used for fixed and mobile radio communication, broadcasting, radar and other navigation systems, communications satellites, computer networks. Also, they are used in Magnetic resonance imaging (MRI) to generate images of the human body. Microwaves, with wavelength ranging from 1 mm to 1 cm, can cause water and fat molecules to vibrate, which makes the substances hot. So, we can use this EM waves to cook many types of food. It is also used in broadcasting and telecommunication transmissions because, due to their short wavelength, highly directional antennas are smaller. Infrared are used for many tasks, for example, remote controls for TVs and video recorders, and physiotherapists use heat lamps to help heal sports injuries. It is used in night vision equipment when there is insufficient visible light to see. Infrared radiation can also be used to remotely determine the temperature of objects. This is termed thermography, or in the case of very hot objects in the NIR or visible it is termed pyrometry. Thermography (thermal imaging) is mainly used in military and industrial applications but the technology is reaching the public market in the form of infrared cameras on cars due to the massively reduced production costs. Visible light is the only electromagnetic wave that we can see. Many of its applications are in optics. The mere fact that we see things is an application of visible light waves. Ultra-Violet light include getting a sun tan, detecting forged bank notes in shops, and hardening some types of dental filling. You also see UV lamps in clubs, where they make your clothes glow. This happens because substances in washing powder "fluoresce" when UV light strikes them - they absorb the UV and then reradiate the energy at a longer wavelength. The lamps are sometimes called "blacklights" because we can't see the UV coming from them. Ultraviolet rays can be used to kill microbes. Hospitals use UV lamps to sterilize surgical equipment and the air in operating theatres. Food and drug companies also use UV lamps to sterilize their products. Suitable doses of Ultraviolet rays cause the body to produce vitamin D, and this is used by doctors to treat vitamin D deficiency and some skin disorders.

X-ray images of the body are an indispensable diagnostic tool in modern medicine. Medical imaging allows for the nonintrusive detection of dental cavities, bone fractures, foreign objects, and diseased conditions such as cancer. X-Rays are also used in airport security checks, to see inside your luggage. They are also used by astronomers - many objects in the universe emit X-rays, which we can detect using suitable radio telescopes. Gamma rays are used in medicine to kill and treat certain types of cancers and tumors. Gamma rays passing through tissue of the body produce ionization in tissue. Gamma rays can harm the cells in our body. The rays can also detect brain and cardiovascular abnormalities. Gamma rays can be used to examine metallic castings or welds in oil pipelines for weak points. The rays pass through the metal and darken a photographic film at places opposite the weak points. In industry, gamma rays are used for detecting internal defects in metal castings and in welded structures. Gamma rays are used to kill pesticides and bugs in food. Gamma rays are also used in nuclear reactors and atomic bombs. Many of these applications are good but sometimes when we are overexposed to some high frequency electromagnetic wave can be dangerous to our health. So we must be cautious when we deal with high frequency electromagnetic waves.

References: 

Regions of the Electromagnetic Spectrum (http://imagine.gsfc.nasa.gov/docs/science/know_l1/spectrum_chart.html)

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https://www.columbia.edu/~vjd1/electromag_spectrum.htm

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https www rscc umn edu rscc v m

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Electromagnetic Waves

html

(http://www.physicsclassroom.com/mmedia/waves/em.cfm) 

Regions of Electromagnetic Spectrum (csep10.phys.utk.edu/astr162/lect/light/spectrum html)

V.

Method/Strategy: Activity Method/Inquiry Approach

VI.

Learning Activities A. Preparatory Activities 1. Greetings 2. Prayer

3. Checking of Attendance 4. Checking of Classroom’s cleanliness and orderliness 5. Review/Recap of past lesson B. Motivational Activities: The teacher will recall some concepts that will be included in the activity. The students should be able to define wavelength, frequency, and energy. C. Developmental Activities 1. After the motivation, the teacher will divide the class into groups. Each group will be consisting of 4 members. This group will serve as their learning circle throughout the activity. 2. The teacher will distribute all the worksheets to the students. Each of them will receive one worksheet. But, the members will help each other in solving the worksheet so that they can finish it fast. 3. The

teacher

will

discuss

some

information

about

the

topic

electromagnetic waves. 4. The students are going to answer the activities within an hour. D. Summary E. Evaluation After an hour of performing and answering the activities, the students are going to check their activity.

Submitted by: Delfin, John Romy P. Penaflor, Raymond B.