                           SCIENCE – GRADE 10
                        ELECTROMAGNETIC WAVES

I. INTRODUCTORY CONCEPT

        We are surrounded with different types of waves and most of them are
invisible but we can perceive some. If you have listened to a radio, watch on a
television, spoke on a cellular phone, had an X-ray taken and felt the warmth of sun
on your skin, then you have experienced electromagnetic wave.

       The world of electromagnetism can be better understood if we will be exposed
to electromagnetic wave equations, where it describes the relationships between
frequency and wavelengths of electromagnetic waves.

II. LEARNING COMPETENCY

       Compare the relative wavelengths of different forms of electromagnetic
        waves.
        (S10FE-IIa-b-47)

        Objectives:
         Trace the development of the electromagnetic wave theory.
         Describe how electromagnetic wave is produced and propagated.
         Explain the relationship between wavelength and frequency of a wave.
         Compute for the frequency and wavelength of a wave.

III. ACTIVITIES

ELICIT:      Let us recall the dispersion of light that you learned in Grade 8. This is
when white light splits into many colors as it passes through a prism, thus creating a
rainbow.




                                          Figure 1. Rainbow
                 Retrieved from https//c75c1f7d944d6d5601e64d6f488967c4--applique-patterns-
                                    parachute.jpg (474×248) (pinimg.com)




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Trivia: A rainbow is caused by sunlight and atmospheric conditions. Light enters a
water droplet, slowing down and bending as it goes from less dense air to denser
water. The light reflects off the inside of the droplet, separating into its component
wavelengths--or colors. When light exits the droplet, it makes a rainbow.
 (Source: https://scijinks.gov/rainbow/#:~:text=A%20rainbow%20is%20caused%20by,droplet%2C%20it%20makes%20a%20rainbow.)




ACTIVITY 1: SHINE LIKE A RAINBOW!

Directions: In the left box below, write the 7 colors of the rainbow arranged based
on decreasing wavelength. In the right box below, write T if the statement about
energy, frequency and wavelength is true and F if the statement is false (1 point
each).

   1.____________                ___1. Red light has the highest frequency.
                                 ___2. Violet has the highest energy.
   2. ORANGE
                                 ___3. Violet has the longest wavelength.
   3.____________                ___4. The higher the frequency of light, the greater the
                                      energy.
   4. GREEN
                                 ___5. The longer the wavelength, the lesser the
   5. ___________                     frequency of light.
                                 ___6. Wavelength is directly proportional to frequency.
   6. INDIGO
                                 ___7. Frequency is inversely proportional to energy.
   7. ____________               ___8. Wavelength is inversely proportional to energy.




ENGAGE:

ACTIVITY 1A: LET’S MATCH THEM!

Directions: Match the scientists given below with their contributions. Write the
letter of the correct answer in the space provided before each number.

        Scientists                                     Contributions

_____1. Ampere                      a. Contributed in developing equations that showed the
                                    relationship of electricity and magnetism
_____2. Faraday                     b. Showed experimental evidence of electromagnetic
                                    waves and their link to light
_____3. Hertz                       c. Demonstrated the magnetic effect based on the
                                          direction of current
_____4. Maxwell                     d. Formulated the principle behind electromagnetic
                                          induction
_____5. Oersted                     e. Showed how a current-carrying wire behaves like a
                                    magnet




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ACTIVITY 1B. LET’S TALK ABOUT EM!

Directions: Write T if the statement is True, F if the statement is false. (1 point each)
______1. Electromagnetic waves transfer energy through vacuum.
______ 2. A wave is a disturbance that transfers energy.
______ 3. Most EM waves are invisible and undetectable.
______ 4. The electric field and the magnetic field oscillate parallel to each other.
______ 5. As wavelength increases, the frequency of wave also increases.

Activity 2: WORK IT OUT.

Given the equation: v = λf
Where: v = speed of light (3 x 108 m/s), λ (wavelength) , f (frequency) , what do you
think will happen to the wavelength of the wave as its frequency increases?
decreases?

Direction: Solve the following problems. Show your solutions.

       Suppose that the waves propagate in a vacuum.

   1. What is the frequency of an electromagnetic with a wavelength of

       A. 1 x 10-3 m?



       B. 3.8 x 10-7 m?


       How do varying wavelengths affect the frequency of a wave?
       ______________________________________________________________
       ______________________________________________________________
       ______________________________________________________________
       ______________________________________________________________
       ______________________________________________________________


   2. What is the wavelength of the wave with a frequency of

       A. 3 x 109 Hz?



       B. 4 x 1014 Hz?


       How do varying frequencies affect the wavelength of a wave?
       ______________________________________________________________
       ______________________________________________________________



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       ______________________________________________________________
EXPLORE
Activity 1. FILL ME UP!
Directions: Complete the concept map.




Electromagnetic worksheet retrieved from https://homeschooldressage.com/wpcontent/uploads/electromagnetic-spectrum-worksheet-
of-electromagnetic-spectrum-worksheet-11.jpg (960×720) (homeschooldressage.com)




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ACTIVITY 2: COMPLETE ME. How do frequencies of electromagnetic waves
compare?
Direction: Complete the table by filling up the wavelengths and frequencies of
various electromagnetic waves. Use the speed of electromagnetic waves - 3 x 108
m/s – and the equation f * λ = c to find the wavelength/frequency of each type of
wave.

      Type of Wave                Wavelength (m)                Frequency (Hz)
  Radio waves                          500 m
  Microwaves                         3 x 10-2 m
  Infrared                                                       1.2 x 1011 Hz
  Visible Light                      8 x 10-7 m
  Ultraviolet Rays                                               6.18 x 1014 Hz
  X-Rays                                                         4.92 x 1016 Hz
  Gamma Ray                          1 x 10-11 m

Guide Questions: Answer the following:
  1. Which wave has the lowest frequency? highest frequency?
  2. Which wave has the shortest wavelength? longest wavelength?
  3. What is the relationship between wavelength and frequency?

EXPLAIN
       In the previous activity, you matched the scientists with their contributions on
the discoveries of electricity and magnetism and the development of Electromagnetic
wave                                                                             theory.
Hoping                                                                    that you got
them                                                                      right. Take a
look at                                                                   this.




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Electromagnetic Waves

        Accelerating electrons produce electromagnetic (EM) waves. These waves
are a combination of electric and magnetic fields. A changing magnetic field
produces an electric field and a changing electric field produces a magnetic field. As
accelerated electrons produce an electric field of a wave, the varying electric field
produces the wave’s magnetic field. Both the electric field and the magnetic field
oscillate perpendicular to each other and to the direction of the propagating wave.
Therefore, electromagnetic waves are transverse waves, as shown in Figure 1.




                              Figure 1. Electromagnetic Wave Propagation
Light Wave Propagation retrieved from https://image3.slideserve.com/6997616/electromagnetic-waves-l.jpg (1024×768) (slideserve.com)


        Among the examples of EM waves are radiowaves, microwaves, infrared,
visible light, ultraviolet, x-rays and gamma rays. All EM waves travel at a speed of
3 X 108 m/s in a vacuum and denoted as c, the speed of light.

      Since all the electromagnetic waves have the same speed, as wavelength
decreases, the frequency of the wave increases as expressed in the equation
                                        v=λf
where: v is the wave speed, or c (speed of light) expressed in meter per second,
       f is the frequency expressed in Hertz
       λ is the wavelength expressed in meters

Speed
      All electromagnetic waves travel at a speed of 300,000 km/s (3 x 108m/s) in a
vacuum of space. However, when electromagnetic waves travel through matter, they
slow down. The speed of the wave depends upon the material they travel through.

      Electromagnetic waves usually travel the slowest in solids and the fastest in
gases, as shown in Table 1 below.




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Frequency

        The frequency, represented by the Greek letter nu (ν), is the number of
waves that pass a certain point in a specified amount of time. Typically, frequency is
measured in units of cycles per second or waves per second. One wave per second
is also called a Hertz (Hz) and in SI units is a reciprocal second (s−1).
Example Problem 1: (Assume that the waves propagate in a vacuum.)
1. What is the frequency of radio waves with wavelength of 20 m?
        Given:        v= c = 3 X 108 m/s
               λ= 20 m
               f= ?
        Equation:
               v=c=λf
        Solution:
               f=c/λ = 3 X108 m/s
                         20 m
               = 1.5 X 107 Hz

Wavelength

       Wavelength is defined as the
distance measured from one crest of a
wave to the next crest or from one
through to the second through or from
one point in any part of the wave to the
next point in the same part.

A wave cycle consists of one complete       https://imgs.edhelper.com/clipart/stories/rstoriesg4925p
wave—starting at the zero point, going      rev.jpg (226×170) (edhelper.com)

up to a wave crest, going back down to
a wave trough, and back to the zero point again. The wavelength of a wave is the
distance between any two corresponding points on adjacent waves. It is easiest to
visualize the wavelength of a wave as the distance from one wave crest to the next.
In an equation, wavelength is represented by the Greek letter lambda (λ). Depending
on the type of wave, wavelength can be measured in meters, centimeters, or
nanometers (1 m = 109 nm). To find wavelength ( λ ), use this equation v=λf

Example Problem 2:
1. What is the wavelength of an electromagnetic wave that has a frequency of
   4.95×1014 Hz?

        Given : f = 4.95 x 1014 Hz
              v= c=3.00 x 108 m/s
              λ =?
        Equation:
              v=λf



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Solution:
λ=v/f
= 3.00 x 108 m/s /4.95 x 1014Hz
= 6.06×10-7 m

ELABORATE
Answer the following questions:

1. What insights did you learn about EM waves?
___________________________________________________________________
___________________________________________________________________

2. How significant is the discovery of EM wave in our life?
___________________________________________________________________
___________________________________________________________________

3. Describe the relationship between frequency and wavelength of the wave.
___________________________________________________________________
___________________________________________________________________

EVALUATION:

MULTIPLE CHOICE: Identify what is asked or describe in each item then write the
letter of the correct answer in your answer sheet.

   1. Who among the scientists below had formulated the Electromagnetic Wave
      Theory?
      A. Ampere                              C. Maxwell
      B. Hertz                               D. Oersted

   2. What can electromagnetic waves travel through that mechanical waves
      cannot travel through?
      A.    Air                             C.    Water
      B.    Wood                            D.    Vacuum

   3. Which of the following statements is incorrect about EM waves?
      A. EM waves have electric and magnetic fields
      B. EM waves vary in speed, frequency, and wavelength.
      C. EM waves form when energy is transferred through field.
      D. EM waves can transfer energy through a medium and vacuum.

   4. An electromagnetic wave is produced by a/an
      A.    dispersion of water wave
      B.    produced by an earthquake
      C.    oscillating electric and magnetic wave
      D.    vibration through air and other medium




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   5. Electromagnetic waves are ________________ waves rather than longitudinal
      waves
       A. compressional                       C. seismic
       B. shear                               D. transverse

   6. What is the frequency of a radio wave with a wavelength of 2.2 m?
      A. 3.0 x 108 Hz                             C. 7.3 x 10-9 Hz
                   8
      B. 1.36 x 10 Hz                             D. 2.2 x 108 Hz

   7. What happens to the wavelength of a wave if frequency is doubled?
      A. the same                                C. halved
      B. doubled                                 D. cannot be determined

   8. Which EM waves carries more energy than the others?
      A. microwaves                             C. UV rays
      B. radio waves                            D. visible light

9. Which of the following is the contribution of Oersted in the development of
Electromagnetic Wave Theory?
       A. demonstrated the magnetic effect based on the direction of current
       B. showed how a current carrying wire behaves like a magnet
       C. showed how experimental evidence of electromagnetic waves and their
          link to light
       D. contributed in developing equations that showed the relationship of
          electricity and magnetism.

10. What is the relationship between wavelength and frequency?
      A. There is an equal value of frequency and wavelength of electromagnetic
          waves.
      B. There is a direct relationship between the frequency and wavelength of
          electromagnetic waves.
      C. There is an inverse relationship between the frequency and wavelength of
          electromagnetic waves.
      D. Cannot be determined.

EXTEND

Directions: Make a Comic Strip about the scientist contributions on the development
of electromagnetic wave theory. Refer to the rubric below for your guidance in
making your output.

   Remember:
   A comic strip is a sequence of drawings in boxes that tell an amusing story, or
   a form of storytelling, which uses drawings or cartoon characters to tell a
   story.




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<div>Watch the video below and answer the questions that follow:</div>

                           SCIENCE – GRADE 10
                        ELECTROMAGNETIC WAVES

I. INTRODUCTORY CONCEPT

        We are surrounded with different types of waves and most of them are
invisible but we can perceive some. If you have listened to a radio, watch on a
television, spoke on a cellular phone, had an X-ray taken and felt the warmth of sun
on your skin, then you