Mirror Lp (3rd Demo)

I.

Objectives At the end of the lesson, the students are expected to: a. describe the appearance of the object in plane mirror in terms of height, width and distance; b. distinguish the different parts of reflection; c. determine the angle of incidence and angle of reflection; and d. explain the functions of optical instrument that uses plane mirrors.

II.

Subject-Matter Topic: Lights: Mirrors and Lenses Sub-topic: Mirrors (plane mirror) Instructional Materials: Visual aids, PowerPoint presentation, illustrations and experiment

III.

Teaching Strategies A. Preparation 1. Routinary Activities a. Praying b. Monitoring of class attendance 2. Review a. Socratic Method

So last meeting, we have discussed about the electromagnetic spectrum and the visible light. In order for me to know if you really understand our topic, can you give me the different regions of electromagnetic? The different regions of electromagnetic are radio, microwave, infrared, ultraviolet, x-ray and gamma ray. Very good! So the different regions are radio, microwave, infrared, ultraviolet, x-ray and gamma ray. How about the different colors of light in electromagnetic spectrum, can you give those? The different colors of light in electromagnetic spectrum are red, orange, yellow, green, blue, indigo and violet. That’s right! The different colors of light in electromagnetic spectrum are red, orange, yellow, green, blue, indigo and violet. .

b. Activity Method So now before we go on to our new topic, I have prepared here an activity for you to answer on the board. Can you please read the direction? Choose the word in the box that satisfy the statement below and write it on the blank provided. Thank you. Now, all you have to do is write the word that satisfy the statement below. The words are in the box. You are going to choose the correct word and write it on the space provided. Direction: Choose the word in the box that satisfy the statement below and write it on the blank provided. Gamma Rays Microwaves Electromagnetic Spectrum Radiowaves

1. ____ can be used to communicate with satellites. 2. ____ have the highest energy of all electromagnetic radiation. 3. The ____ represents the different forms of electromagnetic radiations. 4. ____ are radiowaves of short wavelength. 3. Motivation So now, I think you are all ready for our new lesson. But before that I have prepared here different materials for our experiment today. Can you identify two different materials that you see here on the table? Aluminum foil in the bottle and candles. Thank you. So we have here rolled aluminum foil inserted in a bottle and candles. Aside from those, can you identify another two materials?

Glasses and matchsticks on the table. That’s right. On the table, we have two glasses and matchsticks. How about the last two materials? A box with mirrors and a laser. Now, the box that you see here in front is actually a magic box. So to convince you, I have prepared here an illustration. What did you observe in our illustration? I observe that the beam of light travels in different mirrors. Very good observation. When you turn on the laser light in this point in the box. The light that is produced by this laser will travel in different mirrors in the box. For instance, this s our mirror 1, mirror 2, mirror 3 and mirror 4. For you to better visualize, here is our box and this is our mirror 1, mirror 2, mirror 3 and mirror 4. Now, let’s write on the board your observation on the illustration. The first observation is that the light will hit all the mirrors in the box. And now, what did you observe about the direction of the light? In which mirror do you think the light will hit first? The light will hit first the mirror 2. Very good! Then from mirror 2, it will bounce in what mirror? It will bounce into mirror 4. That’s right it will reflect to mirror 4. Then it will travel into what mirror? It will travel into mirror 1. Correct! Then from mirror 1, it will reflect to what mirror? It will reflect to mirror 3.

Very good! Then from mirror 3, it will reflect back to the source. So these are our observation on the direction. How about the shape? What shape will form from those direction of light? A star- shape will form. That’s right! The path of light will form a star- shape. So now, our task is to determine if all our observations in the illustration is true with our experiment. I have here two bottles with aluminum foil inserted in it. The exposed part of the aluminum foil is twisted. All you have to do is to light 2 candles and allow the flame of these candles to touch the part of aluminum foil that has a twist. Can you do it. Thank you. Now we have another bottle with aluminum foil, can you repeat the procedure? Okay, so what did you observe? I observe that the smoke goes inside the bottle. That’s right! Now, for you to be able to see what will happen, I will divide this class into two. This will be the group 1 and this will be the group 2, and I will proceed on the first group. But before that, can you please turn off the ceiling fan and the light, and also please close the door. Thank you. Now, in this group, please turn on the laser and observe what will happen after pressing this bottle with smoke in the box. Okay, on the second group. Can you turn on the laser, and class, observe what will happen after pouring this smoke inside the box.

What did you observe? The beam of light hits all the mirrors in the box. Very good observation. How about the direction of light? It travels from the source to mirror 2 then mirror 4 then mirror 1 to mirror 3 then back to the source. Exacly! And how about the shape? The shape formed was a star- shape. Correct! So all our observations in the illustration are true and valid. It is because these mirrors and the light follows a physical law in science that we call law of reflection, which is a part of our topic for today which is reflection in mirror.

B. Lesson Proper Now, who among you have watched the movie Snow White and the Seven Dwarfs? What did you observe about the image showed by the mirror, when the queen asked “Mirror, mirror on the wall, who’s the fairest of them all”? The mirror showed the face of Snow White. Exactly, Snow White’s face appear on the mirror! But in reality, is it possible that when you are in front of a mirror the mirror will show different image? No Sir, when you are in front of a mirror, your image will basically what appears in the mirror. Very good! The object in front of the mirror is the image that will appear on it, and that is because of what we called “Reflection” Now,based on your assignment last meeting, how can you define reflection? Reflection is defined as the bouncing of light as it hits an object.

That’s right. As you observed in our experiment, the beam of light hits one mirror then reflected into other mirrors. In that experiment, we can say that reflection takes place because the light bounces off from one mirror to another. Now, there are different types of mirror that shows different orientation of an object. The mirror that we used in our experiment is what we call plane mirror. This mirror is usually the kind of mirror that we are using. So our task now is to know the relationship among the object and the image formed in the mirror. I will divide this group into two, this is group1 and this is group 2. So now we have here different materials. Can you identify two different materials? Plane mirrors and graphing paper, How about the materials left? Ruler, clay and stack of 10 pieces of one-peso coin. Very good. So now, here is our procedure, can you please read? Step 1. Let the mirror stand vertically along a line on a graphing paper. Step2. By using a pen, make three different marks along the intersection. Step 3. Measure the distance of each mark from the mirror by counting the number of parallel lines between the mark and the base of the plane mirror. Record your data in a table similar to Table 1 below. Step 4. Look at the images of the marks formed by the mirror. Measure the distance of each image from the mirror by counting the number of parallel lines between the image and the base of the mirror. Record this also in Table 1.

Table 1. Distance of the Object and Image from the Mirror Number of Parallel Lines Mark

Between the mark and the Mirror

Between the image and the Mirror

Mark 1 Mark 2 Mark 3 Ok class, for the second part of our activity here is the procedure, can you please read? Step 5. Stack 10 pieces of one-peso coin in front of the plane mirror as in Figure 2. Using a ruler, measure the height and width of the stack of coins. Measure also the height and width of the image as seen on the mirror. Enter your measurements in a table similar to table 2. (Illustration)

Table 2. Height and Width of Object and Image

So class, on the first part of the activity, how did you compare the distance from the mirror of the object?

Very good! How about on the second part? How did you compare the height and width of the object compare with the height and width of the image?

Description Height (cm) Width (cm)

Object

Image

The image formed in the mirror has the same number of parallel lines with the object.

The height and the width of the object is the same with the height and the width of the image.

That’s right! So what would be our conclusion with the relationship of the object in the plane mirror? The plane mirror produces an image that has the same distance, height and width as the object Very good! So it means that when you stand 2m in front of a plane mirror, the image in the mirror will also appear 2m.

Now, let us move on to our next topic that still discuss about the reflection of light in a plane mirror, the angle of incidence and angle of reflection. I have here a set of words and illustration. Can you read those words? Incident ray, reflected ray and normal line. Thank you. So before we define those words, let us first define what is ray in physics. Can you define what is ray? (insert a picture figure of incident ray, reflected ray, and normal line) Ray is an idealized model of line that is perpendicular to the lights wave fronts. Very Good! In addition to that, a light ray is a model of light that are draw as a straight line. Now, let us now proceed to our first word, incident ray, what is incidents ray? Incident ray is a ray of light approaching the mirror represented by an arrow approaching an optical element like mirror. Excellent! And to make it simple, an incident ray is ray of light that is pointing towards and striking a surface. Example, if you throw a ball onto the surface, you throw it and that led to it hitting the surface. Same with the light hitting the surface of the plane mirror. (insert a picture of incident ray)

How about the reflected ray? Reflected ray is ray of light which leaves the mirror. Nice. When the light hits the plane mirror, some of it can be absorbed and some of it can be reflected, like what he/she said, it leaves the mirror. Very good! (insert a picture of reflected ray) The last word that we have here is the normal line, it is the imaginary line that can be drawn perpendicular to the surface of the mirror at the point of incidence where the ray strikes the mirror. (insert picture of normal line) So class, I guess you are all know the difference of incident ray, refracted ray and the normal line. Let us have another activity entitled “angle of incidence vs. the angle of reflection” Angle of incidence is the angle between the incident ray and the normal line while the angle of reflection is the angle between reflected ray and normal line. Are we clear? Yes ma’am/sir! So let us begin, kindly tell what are the materials? The materials are, plane mirror, low frequency laser/laser pen/laser pointer, paper protractor. Thank you, how about the procedures, kindly read them? Step 1. Let the mirror stand vertically along the edge of the paper protractor as shown in figure 4. Use the clay to support the plane mirror. (insert figure 4) Step 2. Position the laser beams such that it hits the mirror at an angle of 10˚ with the

normal line. Measure the angle between the reflected ray and the normal line. Record your measurements in a table similar to table 3. Table 3. Angle of Trial incidence 1 10 ˚ 20 ˚ 30 ˚ 40 ˚ 50 ˚

Trial 2

Trial 3

Ave.

Step 3. Make three trials and get the average. Step 4. Repeat the steps 2 to 4 for angles 20 ˚, 30 ˚, 40 ˚ and 50 ˚. Enter all your measurements in table 3. Thank you! Are you all ready? Yes ma’am/sir! (the students will do the activity) (after the activity) Now, what did you observe after our second activity, how does the angle of incidence compare with the angle of reflection, Nicole?

Very well said Nicole, they are equal, and note that, that is one of the law of reflection, which states that angle of incidence is equal to the angle of reflection

The angle of incidence is equal to the angle of reflection.

Now, let us explore more about plane mirror. Some mirror produces an image that is reverse of its actual image. Let us see if our plane mirror exhibits such characteristic. I have here different material for our third activity. Can you identify them? An alphabet chart and a plane mirror.

Thank you. Now, what you are going to do is to place the alphabet chart in front of plane mirror and identify all capital letters in the alphabet that can be read properly in front of a mirror. After that, write at least three (3) words in capital letters that can be read that can be read properly both with a mirror and without a mirror in front of it. Okay, so class what are the letters that can be read properly in front of the mirror? The letter that can be read properly in front of the mirror are A, H, I, M, O, U, V, W, X and Y Very well said. How about the words that can be read properly with or without a mirror. Can you give me one? HOW Very good, another word? WAX That’s right. Another one. HAM Correct. Another one? AIM Very good! So those are the words that can be read properly with or without a mirror. So, what did you observe with the other letters in front of the mirror, why can’t you read them properly? We cannot read the other letters properly because they appear in reverse in front of the mirror. Very good! So when you stand in front of the plane mirror and you raise your left hand, the image in the mirror will raise his right hand. The left

side of the object appears as the right side of the mirror. What did you observe in the word ambulance in an ambulance car? The word is written in reverse. That’s right! So what it is implication with the mirror that we use? This is written in reverse so that it will appear properly on the mirror of the cars in front and beside it. That’s correct! So that the other cars’ mirror will produce the image of “ambulance”. That can be properly read by the driver. In such case, they will make way for the ambulance car. C. Generalization So to sum it up, what is the relationship between the object and the image formed in plane mirrors in terms of distance, height and width of an object? The objects’ height, width and distance from the mirror is the same as the height, width and distance of the image formed in the plane mirror. Very good! How about the relationship between angle of incidence and angle of reflection? The angle of incidence is equal to the angle of reflection. That’s correct! And that statement is under what physical law in science? Law of reflection. That’s right. How about what happened to the orientation of the image in the plane mirror? The image is in reverse manner. Very good.

D. Application Now that we have learned about the plane mirror together with the image formed, what do you think is the reason why plane mirror is always used in the fitting room?

That’s correct. In addition, plane mirrors are also used in construction of periscopes which is used in submarines, solar cooker and also used to make kaleidoscope, a toy which produces beautiful patterns from colored paper, pieces of glass or small colored beads. IV. Evaluation I think you have learned a lot today about mirrors so get ¼ sheet of paper and let us have a short quiz. SHORT ANSWER: 1. The angle between the incident ray and the normal line. 2. The angle between the reflected ray and the normal line. 3. The bouncing off of light rays when it hits a surface. 4. The imaginary line to the surface of the mirror. 5. The ray of light represented by an arrow pointing away from mirror. V.

Assignment 1. What is multiple images? 2. What are the different types of reflection? 3. What are the different types of spherical mirrors? Give three examples each

Plane mirror is used in the fitting room because it gives an image the same size with the object. Through this, the person who looks in the mirror will be able to see if the dress looks well in him.