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CONTENTS MOduleone

MODULE 1 Getting Hooked on Electricity and Magnetism Application The Principle of Induced Magnetism Electromagnetic Induction

MODULE 2 Electromagnetic Spectrum The Radio Waves Infrared Waves Ultraviolet Waves

MODULE 3 The Reflection of Light in Mirrors Images that are Formed by Curved Mirrors The Refraction of Light in Lenses

EXTRA TOPICS Electromagnetic Spectrum Visible Light Gamma Rays

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MOduleone

force, motion, and energy

eople readily adopt emerging technologies. The use of audiovisual (AV) works be it in film produc-tions, in business displays, or perhaps in education innovations became a trend and it is here to stay.

Examples abound like our growing love for the high qual-ity audiovisual components we listen to and watch or the endeavor of school stakeholders to provide projection technology in every classroom. The rise of it all AV production, recording, and storing technology and industries were made possible because of the discovery of the link between electricity and magnetism. How does one begin to understand this partnership? Most of the devices found in a typical AV studio often uses both electricity and magnetism. They use elec-tricity for power, while a magnet can be used to vary the magnetic force by changing the amount and direction of the current going through the coils or windings around it. Loudspeakers and tape recorders are devices that often apply this effect.

MODULE 1

GETTING HOOKED ONELECTRICITYAND MAGNETISMAPPLICATION

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A typical broadcast studio consists of an audio console, mi-crophones, computers, studio monitors, and disc players. The audio console converts analog audio (voice via mi-crophone) and phone calls to a digital output. It also allows for the mixing of all sound sources from CDs, computers, and other digital sources before being sent to the transmitter. A slider controls the volume of each sound source. The live audio and control rooms are connected by cables for the exchange of audio and digital data signal during recording, mixing, and even editing of all audio-video elements digitally stored on hard drives. Many of the recording technology are founded entirely or partially on the relationship between electricity and magnetism known as electromagnetic induction. Devices that detect and convert audio inputs to electric outputs or vice versa are called transducers. Most transducers like microphones and speakers use the “generator effect” character-ized by the production of forces due to a changing electric signal within a magnetic field or a changing field near a current-carrying conductor.

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EvaluationA. Determine whether the following devices need electricity, magnetism, or both. Write A if it uses electricity, B if it uses magnetism, and C if it uses both electricity and magnetism.

_____ 1. Microphone_____ 2.Speakers_____ 3.Audio console

_____ 4. Studio monitor_____ 5. CPU_____ 6. Spotlight

B. Fill in the blanks with the correct answer.

1. The ____________ converts analog audio and phone calls to a digital output.2. A ____________ is used to connect and exchange of audio and digital data signal during recording, mixing and editing.3. The ____________ is the relationship between electricity and magnetism.4. Devices that detect and convert audio inputs to electric outputs or vice versa are called ____________.

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he magnetism acquired by magnetic material while it is in a magnetic field. When a piece of unmagnetised magnetic materi-al touches or is brought near to the pole of a per-

manent magnet, it becomes a magnet itself. The magne-tism is induced. A North pole induces a North pole in the far end. It is a process by which magnetic objects become magnets. This same process is the reason why a magnet can attract, for example, a screw which is a non-magne-tized magnetic substance.

MODULE 1

the principle of

inducedmagnetism

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Evaluation Now that you’ve learned the concept of innduced magnetism, it is your time to shine! Give another example of induced magnetism that is applied in real life and is a big help to our lives.

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lectromagnetic induction is the production of an electromotive force across a conductor when it is exposed to a time varying magnetic field. It is de-scribed mathematically by Faraday’s law of induc-

tion, named after Michael Faraday, who is generally cred-ited with the discovery of induction in 1831. Electromagnetic induction was first discovered by Michael Faraday, who made his discovery public in 1831.[2][3] It was discovered independently by Joseph Henry in 1832.

MODULE 1

electro-magneticinduction

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The magnetic flux developed around the coil being pro-portional to the amount of current flowing in the coils windings as shown. If additional layers of wire are wound upon the same coil with the same current flowing through them, the static magnetic field strength would be increased. Therefore, the Magnetic Field Strength of a coil is deter-mined by the ampere turns of the coil. With more turns of wire within the coil, the greater the strength of the static magnetic field around it.

MOduletwo

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Evaluation

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Identify the parts of the illustration. (2 points each)

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MOduletwo

electromagnetic spectrum

adio waves have the longest wavelength in the electromagnetic spectrum. They are produced by making electrons vibrate in an antenna. They are used to transmit sound and picture information

over long distances. Radio waves have a very wide range of wave-lengths. The whole region of the radio waves is divided into smaller regions or wavebands. Each waveband is allocated by law to a specific radio service. (Refer to the table on the next page)

MODULE 2electromagneticspectrum:the radiowaves

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Low frequency waves are suitable for communication over great distances. But the curvature of the earth limits the range to about 80 kilometers. To extend the range, a repeater is used. The repeater receives the signal and re-transmits it to the receiving sta-tion. High frequency waves can be reflected by the ionosphere. This enables the waves to be transmitted over great distances. 152 Medium and high frequency waves are used for broadcast-ing by local radio stations. In a radio station, sound is converted by a microphone into patterns of electric current variations called au-dio-frequency (AF) signals. High frequency radio waves called ra-dio-frequency (RF) carriers can be modulated to match the elec-tronic signal. In amplitude modulation, the amplitude of the radio waves (RF carrier) changes to match that of the audio-frequency signal. This is used in standard broadcasting because it can be sent over long distances. Very high frequency waves provide a higher quality broadcasting including stereo sound. In this process, instead of the amplitude of the RF carrier, it is the frequency of the waves that changes to match that of the signal. This is called frequency modulation.

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Evaluation

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Complete the paragraph by filling in the appropriate terminologies. (2 points each)

Radio waves have the ________ wavelength in the electromagnetic spectrum. They are produced by making electrons _______ in an antenna. They are used to transmit sound and picture information over _______ distances. Radio waves have a very _____ range of wavelengths. The whole region of the radio waves is divided into smaller regions or _______. Each waveband is allocated by law to a specific radio service.

nfrared radiation lies beyond the red end of the visi-ble light. It is emitted by all objects. The amount and wavelength of radiation depend on temperature. Be-low 500oC, an object emits only infrared radiation.

Above 500oC, an object glows and emits both infrared and some visible light. Our bodies radiate infrared and under infrared camera or a night vision goggle, our images appear in variety of colors. The differences in color determine the differences in temperature. For example, shades of blue and green indicate regions of colder temperature; and red and yellow indicate warmer temperature.

MODULE 2electromagneticspectrum:infraredwaves

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The following are some useful applications of IR radiation:

1. Infrared photographs taken from a satellite with special films provide useful details of the vegetation on the Earth’s surface. 2. Infrared scanners are used to show the temperature variation of the body. This can be used for medical diagnosis. 3. Infrared remote controls are used in TVs, video, cas-sette recorders, and other electronic appliances. 4. Some night-vision goggles use IR. 5. Some autofocus cameras have transmitter that sends out infrared pulses. The pulses are reflected by the object to be photographed back to the camera. The distance of the object is calculated by the time lag between the sending and receiving of pulses. The lens is then driven by a built-in motor to adjust to get the correct focus of the object.

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EvaluationState whether the following statements are true or false. Write I if true, and write J if false.

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_____ 1. Infrared rays can be emitted by living things._____ 2. All objects emit infrared radiation._____ 3. The difference in the color produced determines the varying frequency._____ 4. Infrared photographs taken from a satellite with special films provide useful details of the Earth’s weather._____ 5. IR can be used for medical diagnosis._____ 6. Remote controls use infrared rays._____ 7. Infrared rays are found in all night-vision goggles._____ 8. Some autofocus cameras have transmitter that sends out infrared pulses._____ 9. Pulses are refracted by objects to be photographed back to the camera. ____ 10. Infrared radiation has no help to our lives.

ltraviolet radiation lies just beyond the violet end of the visible spectrum. Ultraviolet waves have shorter wavelengths than the visible light and car-ry more energy.

Ultraviolet (UV) light is an electromagnetic radia-tion with a wavelength from 400 nm to 100 nm, shorter than that of visible light but longer than X-rays.

MODULE 2electromagneticspectrum:ultravioletwaves

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The sun is our main source of ultraviolet radiation but there are also artificial sources of UV light. Ultraviolet radiation in UV lamps are used by banks to check the signature on a passbook. The signature is marked on the passbook with fluorescent ink. It be-comes visible when viewed under an ultraviolet lamp. These lamps are also used to identify fake banknotes. Ultraviolet radiation is also used in sterilizing water from drinking fountains. Some washing powder also contains fluorescent chemicals which glow in sunlight. This makes your shirt look whiter than white in daylight. Ultraviolet radiation in sunlight produces vitamin D in the skin and gives us tanning effect. But since UV rays have high energy, it could be harmful to some extent. It could burn the skin and hurt our eyes. Overexposure to UV radiation may cause skin cancer. Suntan or sunscreen lotions serve as filters to protect the body from ultra-violet radiation.

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EvaluationCite ten uses/applications of ultraviolet rays to our lives which is considered helpful in terms of good use.

1.2.3.4.5.6.7.8.9.10.

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MOdulethree

light: mirrors & lenses

hen people look into a mirror, they see an im-age of themselves behind the glass. That im-age results from light rays encountering the shiny surface and bouncing back, or reflecting,

providing a “mirror image.” People commonly think of the reflection as being reversed left to right; however, this is a misconception. If you face north and look straight into a mirror, the east side of your face is still on the east side of the image, and the same is true for the west side. The mirror does not reverse the image left to right; it reverses it front to back. For example, if you are facing north, your reflection is facing south. The reflection of light rays is one of the major aspects of geometric optics; the other is refraction, or the bending of light rays. Geometric optics is one of two broad classes of optics, the field that “deals with the prop-agation of light through transparent media,” according to Richard Fitzpatrick, a professor of physics at the Uni-versity of Texas at Austin, in lecture notes for a course in Electromagnetism and Optics. (The other class is physical optics.)

MODULE 3

the reflection

of lightin mirrors

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Reflection is the bouncing off of light rays when it hits a sur-face like a plane mirror. In the activity, you used plane mirrors and located the object distance, p and the image distance, q and found out that p is equal to q. In plane mirrors, the image appears as if it is behind the mirror but actually not, so the image is virtual. The value therefore of image distance, q is negative. The height of the image, h’ in plane mirrors is always the same as the height of the object, thus its magnification, M is 1. The magnification formula is written below:

Incident Ray. The ray of light approaching the mirror repre-sented by an arrow approaching an optical element like mirrors. Reflected Ray. The ray of light which leaves the mirror and is represented by an arrow pointing away from the mirror. Normal Line. An imaginary line that can be drawn perpen-dicular to the surface of the mirror at the point of incidence where the ray strikes the mirror. The angle between the incident ray and the normal line is known as the angle of incidence, Ө i. The angle between the reflect-ed ray and the normal is known as the angle of reflection, Өr.

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EvaluationMatch the words in column A with a proper terminology in column B. A B

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1. Image resulting from light rays encounter-ing the shiny surface and bouncing back, or reflecting2. The way the mirror is reversed3. Ray of light which leaves the mirror4. Misconcepted reversal5. Image that our eyes see6. Ray of light approaching the mirror7.Imaginary line perpendicular to the surface of the mirror at the point of incidence8. Angle between the incident ray and the normal line9.Angle between the reflected ray and the normal ray10. The bouncing off of light rays when it hits a surface like a plane mirror

A. Reflected RayB. ReflectionC. Angle of IncidenceD. ApparentE. Normal LineF. Angle of ReflectionG. Left-RightH. Front-BackI. Mirror ImageJ. Incident Ray

curved mirror is a mirror with a curved reflecting surface. The surface may be either convex (bulg-ing outward) or concave (bulging inward). Most curved mirrors have surfaces that are shaped like

part of a sphere, but other shapes are sometimes used in optical devices. The most common non-spherical type are parabolic reflectors, found in optical devices such as reflecting telescopes that need to image distant objects, since spherical mirror systems, like spherical lenses, suffer from spherical aberration. One advantage that mirror op-tics have over lens optics is that mirrors do not introduce chromatic aberration.

MODULE 3

the images thatare formed by

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In locating the image formed in curved mirror graphically, three im-portant points are considered. • Center of Curvature, C - the center of the sphere of which the mirror is part. Its distance from the mirror is known as the radius. • Vertex, V - the center of the mirror. • Focal Point/ Focus, F - the point between the center of the curvature and vertex. Its distance from the mirror is known as the focal length, f.

The ‘Four Principal Rays’ in Curved Mirrors Images formed in a curved mirror can be located and de-scribed through ray diagramming. The P – F ray, F – P ray, C – C ray, and the V ray are the ‘Four Principal Rays’ in curve mirrors. These rays, applied for concave and convex mirrors, are presented in Ta-ble 5.

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In determining the position and nature of the image graphi-cally, the ‘Four Principal Rays’ are used. Ray diagramming is used in the graphical method of locating the image. The following are ray diagramming steps using the ‘Four Principal Rays’ in determining the position and the nature of the image of an object formed by concave mirror and convex mirror. 1. From the object, draw the first ray (P – F ray). From the same point on the object, draw the second (F – P ray), third (C – C ray), and fourth (V ray) rays. 2. The intersection of the four rays is the image point corre-sponding to the object point. For example, if you started diagram-ming from the tip of the arrow-shaped object, the intersection of the reflected rays is also the tip of the arrow-shaped image. Thus, you can determine completely the position and characteristics of the image. 3. For a convex mirror, light rays diverge after reflection and converge from a point that seems to be behind the mirror (virtu-al focus); but the procedure for locating images is the same as for concave mirror.

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EvaluationAnswer the following questions as briefly as possible. (2 points each)

1. What is a P-F Ray for a Converging mirror? for a Diverging mirror?

2. What is an F-P Ray for a Converging mirror? for a Diverging mirror?

3. What is a C-C Ray for a Converging mirror? for a Diverging mirror?

4. What is a V Ray for a Converging mirror? for a Diverging mirror?

5. What is the difference of the rays between a Converging and a Diverging mirror?

insightsinsights

enses are found in a huge array of optical instru-ments, ranging from the simple magnifying glass to a camera lens to the lens of the human eye. The word lens derives from the Latin word for lentil

bean—the shape of which is similar to that of the convex lens (as shown in ). The convex lens is shaped so that all light rays that enter it parallel to its axis cross one anoth-er at a single point on the opposite side of the lens. The axis is defined as a line normal to the lens at its center (as shown in ). Such a lens is called a converging (or convex) lens for the corresponding effect it has on light rays. The expanded view of the path of one ray through the lens illustrates how the ray changes direction both as it enters and as it leaves the lens.

MODULE 3

the refraction

of lightin lenses

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Recall that the a ray will bend as it enters a medium with a different refractive index. Since the refractive index of a lens is greater than air, a light ray will move towards the perpendicular as it enters and away as it leaves. A convex lens has been shaped so that all light rays that enter it parallel to its axis cross one another at a single point on the opposite side of the lens (the focal point). Such a lens is called a converging (or convex) lens for the converging effect it has on light rays. See. A concave lens is a diverging lens, because it causes the light rays to bend away (diverge) from its axis. shows the effect it has on rays of light that enter it parallel to its axis (the path taken by ray 2 in the figure is the axis of the lens). The greater effect a lens has on light rays, the more power-ful it is said to be. A powerful converging lens will focus parallel light rays closer to itself and will have a smaller focal length than a weak lens. The power of a lens is given by the equation

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EvaluationAnswer the following questions in one sentence.

1. What is a convex lens? (1 point)

2. What is a concave lens? (1 point)

3. Differentiate a convex lens and a concave lens from each other. (2 points)

4. What is the relation of light rays to a lens? (2 points)

5. What is the importance of lenses? (4 points)

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extraextraextraTopics

hen white light passes through a prism, it is separated into its constituent colors: the red, orange, yellow, green, blue, indigo and violet. These colors do not distinctly separate but

they continuously change from red to violet. Red color has the longest wavelength from among these colors and violet has the shortest

MODULE 2electromagneticspectrum:visiblelight

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Our eyes are sensitive to electromagnetic waves of wave-lengths that ranges from 4x10-7 m to 7x10-7 m. This is the range of wavelengths of white light. Thus, the spectrum of white light is there-fore called the visible spectrum.

amma rays lie at the other end of the electromag-netic spectrum. They are shortest in wavelength and highest in frequency. They carry the highest amount of energy, thus, they are more dangerous.

Gamma rays are emitted by stars and some radioactive substances. They can only be blocked with lead and thick concrete. Gamma rays are very strong that they can kill liv-ing cells. Gamma rays are used to treat cancer through the process called radiotherapy. They are also used for sterilization of drinking water.

MODULE 2electromagneticspectrum:gammarays

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Gamma radiation, also known as gamma rays, and denot-ed by the Greek letter Ө, refers to electromagnetic radiation of an extremely high frequency and therefore consists of high-energy photons. Gamma rays are ionizing radiation, and are thus biolog-ically hazardous. They are classically produced by the decay of atomic nuclei as they transition from a high energy state to a lower state known as gamma decay, but may also be produced by other processes. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from ra-dium. Villard’s radiation was named “gamma rays” by Ernest Ruth-erford in 1903. Natural sources of gamma rays on Earth include gamma decay from naturally occurring radioisotopes, and secondary radi-ation from atmospheric interactions with cosmic ray particles. Rare terrestrial natural sources produce gamma rays that are not of a nuclear origin, such as lightning strikes and terrestrial gamma-ray flashes. Additionally, gamma rays are produced by a number of astronomical processes in which very high-energy electrons are produced, that in turn cause secondary gamma rays via brems-strahlung, inverse Compton scattering, and synchrotron radiation. However, a large fraction of such astronomical gamma rays are screened by Earth’s atmosphere and can only be detected by spacecraft.

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ANSWERSMODULE 1

Getting Hooked on Electricity and Magnetism Application

A.1. C 4. C2. C 5. C3. C 6. C

B.1. Audio console2. Cable3. Electromagnetic induction4. Transducers

The Principle of Induced Magnetism

( to be evaluated by the author )

Electromagnetic Induction

1. Lines of Flux2. Coil3. Induced emf4. Rotating magnetic field5. Rotating shaft

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ANSWERSMODULE 2

Electromagnetic Spectrum The Radio Waves

1. Longest2. Vibrate3. Long4. Wide5. Wavebands

Electromagnetic Spectrum Infrared Waves

1. I2. I3. J4. J5. I6. I7. J8. I9. J10. J

Electromagnetic Spectrum Ultraviolet Waves

( to be evaluated by the author )

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ANSWERSMODULE 3

The Reflection of Light in Mirrors

1.I 6. J2. H 7. E3. A 8. C4. G 9. F5. D 10. B

Images that are Formed by Curved Mirrors

( to be evaluated by the author )

The Refraction of Light in Lenses

1. A convex lens has been shaped so that all light rays that enter it parallel to its axis cross one another at a single point on the opposite side of the lens (the focal point). Such a lens is called a converging (or convex) lens for the converging effect it has on light rays. See.2. A concave lens is a diverging lens, because it causes the light rays to bend away (diverge) from its axis. shows the effect it has on rays of light that enter it parallel to its axis (the path taken by ray 2 in the figure is the axis of the lens).3. ( to be evaluated by the author )4. The greater effect a lens has on light rays, the more powerful it is said to be. A powerful converging lens will focus parallel light rays closer to itself and will have a smaller focal length than a weak lens. The power of a lens is given by the equation.5. ( to be evaluated by the author )