PH 221 Grantham University Week 6 Lenses and Mirrors Lab Report

PH 221

Grantham University


Question Description

PH221 – Week 6 Lab

Lenses and Mirrors

Welcome to the Lab component of Physics II. All our labs use simulation applications of real laboratory equipment that are combined with measurement and graphing tools to allow you to explore, observe and analyze experiments. Each week you will complete one laboratory exercise using a virtual lab application and then use your results to write a formal lab report. Each experiment will be based around one main topic.

For this week’s lab you will use the Lenses & Mirrors simulation. Download and read the following user guide to familiarize yourself with the simulation.

Lenses & Mirrors User’s Guide

Download the instructions for two laboratory activities you will complete this week. You may wish to print them out and use to collect and organize your results.

Image Formation by Plane and Spherical Mirrors Lab

Use the answers to the laboratory questions to help you write your lab report. Your report will focus on Parts I and II of the lab. You should discuss the properties of the image obtained for different object positions.

The lab report will have the following six sections. Include section headings in bold at the beginning of each section.

1.Introduction – Explain the purpose of this laboratory and what results you expect to see in this experiment.

2.Background – Discuss the concepts that form the foundation for this lab. You should address what you learned from the weekly lectures and readings that are related to the lab.

3.Methodology – Describe the apparatus that was used in the experiment(s) and how it was used in performing the experiments. Also explain what tools were available within the laboratory that allowed you to collect or analyze the data.

4.Data – Enter the data that you collected in the lab. You can use screen shots from the Data Table within the Pivot Interactives labs. Data should be clearly labeled with physical quantities and units.

5.Analysis – Analyze your results. If your Data Table included Calculated Columns, then the equation you used in those calculations should be included and described here. Any graphs created with the data go in this section, as well as your interpretations of their meaning. Were your results consistent with your original expectations?

6.Conclusion – Provide a concise summary of the results of your experiment(s) – what you did, what you found and what it means. Speculate on possible sources of experimental error and/or uncertainty within the experiment. Describe an additional experiment that could be run with this equipment to expand on what you’ve learned OR explain how you could use this equipment to answer another real-world problem.

PH221: Rubric for Laboratory Assignment 6


If a PDF file is used, name and GID must be on each page.

All of most of the screenshots are missing.

Screenshots lack a time stamp (when indicated)

Lab worksheet file(s) not submitted along with the lab report.

The following screenshots required with a computer timestamp included:






Lab Report

The lab report should focus only on the experiments in Parts I and II of the Image Formation by Plane and Spherical Mirrors lab.



The purpose of the lab is clearly stated and is aligned with the lab objectives. Expected results are proposed.


The purpose of the lab and expected results are stated and consistent with the assignment.


The purpose of the lab and expected results are stated but lacks clarity or is not consistent with the assignment.


The stated purpose is not aligned with the lab objectives or missing key elements.


The introduction is missing.



The concepts that form the foundation of the lab are discussed. Reference to the weekly lectures or readings are made.


Concepts that underly the lab are discussed, but no reference is made to the weekly lectures or readings.


Concepts that relate to the lab are discussed but are vague or contain minor errors.


Underlying concepts are described but reveal major errors in understanding.


The background was not addressed


-Include a screenshot of the optics bench apparatus and description of how it works.


Methods, materials and equipment are specifically described using proper terminology. Concise, but detailed, procedure is provided.


Methods, materials and equipment are described, and a detailed procedure provided, but minor errors in terminology or descriptions are made.


Materials, methods and equipment are described, and a procedure provided, but they are too brief or vague to easily follow.


Some materials, methods and procedures are described, but they are not coherent or missing major pieces.


The methodology was not provided.


Include the Screenshots:







Adequate data is collected in the lab is presented in a logical way that is organized and clear. Data is relevant to the purpose of the lab. Tables and observations are complete, clearly labeled, and physical quantities and units are given when appropriate.


Adequate data is provided and relevant to the purpose of the lab, but with minor errors in labeling or units. Tables and observations are complete and generally include captions and units.


Relevant data is provided, but it is not adequate to address the purpose of the lab or contain errors or omissions so that it is difficult to derive useful information from the data.


Data provided is not relevant to the purpose of the lab. Data is not organized or major errors in labeling and units appear throughout.


Little to no organization of the data was present. Lacks data.



-Description of image properties when the object is located at different positions relative to the focal point.


Data is analyzed appropriately, and key results are presented in a logical sequence. All required calculations are included. Sample calculation(s) are provided to show how the calculations were done. All variables include units when appropriate.


Data is analyzed, but with some details missing. All required calculations are included but with minor errors.


Data is analyzed, but with key details missing or inaccurate. One of the required calculations is missing or major mistakes made in the calculations.


Data analysis is included but does not include the required calculations or major errors in the calculations are made.


Date analysis is lacking.



Conclusion contains a concise summary of the results, speculates on the possible sources of error and uncertainty in the lab, and proposes an experimental extension of the lab or applies its concepts to a real-world situation.


Conclusion is provided, but only two of three elements are well addressed.


Conclusion is provided but only summarizes the results.


A conclusion is provided, but does not communicate useful information about the results, sources of error or possible laboratory extensions.


A conclusion was not provided

Unformatted Attachment Preview

KET Virtual Physics Labs KET © 2019 Name School ____________________________________ Date Image Formation by Plane and Spherical Mirrors Purpose • To become familiar with the nature of the images formed by plane and spherical mirrors. • To learn to distinguish between real and virtual images. • To discover the relationships among object position, image position, focal length, magnification, and the radius of curvature of plane, converging, and diverging mirrors. • To become familiar with sign conventions and how and why they’re used. Equipment Virtual Optical Bench PENCIL Explore the Apparatus/Theory Open the Virtual Optical Bench Lab Figure 1: Optical Bench Apparatus The virtual Optical Bench Apparatus simulates the formation of images by plane mirrors and by converging and diverging mirrors and lenses. We’ll focus on mirrors in this lab. Were it not for the development of eyes, there wouldn’t be a lot to say about the interaction of light with reflective and refractive media except that it sometimes reflects and sometimes refracts, and sometimes does both. But because of the wondrous way that our eyes can take the light leaving an object and reconstruct a replica of that object on our retinas which can then inform the brain of the original object, we have developed the powerful study of optics. Everyone is very familiar with the plane mirror and has had at least some experience with curved mirrors and lenses in a number of settings. From our extensive experience with our daily primping we feel very confident with the use of plane mirrors. But when we first try to use a car’s rear-view mirrors, we find that we a have a lot more to learn. VPL_Lab -Mirrors-Images 1 Rev 12/19/18 KET Virtual Physics Labs KET © 2019 When you start up the Optical Bench Apparatus it should look like Figure 1. A dashed line has been added in Figure 1 that separates two parts of the apparatus. Below the line is the Ray Optics Tool where light rays are used to show the geometry involved in the formation of images. Above the dashed line is the Optical Bench and its object and image tools and screens. The Ray Optics Tool serves another important function: it controls the Optical Bench. Let’s try it with the concave (converging) mirror. Move your pointer over each of the five lenses and mirrors. The info box will identify each one and tell you how to switch choices. Click and drag the plane mirror until your pointer is over the concave mirror (below on the Ray Optics Tool) and release. The concave mirror should be replaced by the plane mirror. If not, try again. Remember, your pointer needs to be over the device being replaced when you release the button. Now swap them back. We want to work with the concave mirror. To the left of the mirror are two vertical arrows. The one pointing upward with the small light blue drag handle on the bottom is the Object Arrow. It represents whatever object we’re working with. As suggested by Figure 2 it emits light in all directions. Actually light is emitted in this way from every point on the object. We display only two (sometimes three) of these rays. Drag the Object Arrow from side to side as far as you can. You’ll see that the rays are continually redrawn, and the other arrow, the Image Arrow, can move, resize and flip vertically. Figure 2: Object Arrow There’s also action on the Optical Bench. Notice how the little box with the cow on the front moves in sync with the Object Arrow on the Ray Optics Tool. That’s the Optical Bench’s object. It’s a slide illuminated from behind. Thus it emits light rays in all directions. Leave the object somewhere near the back end of the Optical Bench. You’ve seen that the Image Arrow on the Ray Optics Tool moves, flips, and changes size. To let us see the image on the Optical Bench, we allow light from the object to illuminate a screen. To form an image on the translucent screen, it must be moved to where the image is located. You’ll examine that concept in detail soon. The Screen Position Tool on the Ray Optics Tool is used to move the screen on the Optical Bench. It’s a vertical gray line with a semicircular handle at one end. Drag it from side to side and notice how the screen moves on the Optical Bench. Also notice, that when it’s to the left of the concave mirror a smudge of light appears on the screen. Figure 3: Screen Position Tool As you move the object, the smudge looks more or less like an inverted cow, depending on the location of the object. Leave the screen somewhere between the mirror and the object. If you have for some reason changed the Mirror/Lens Number to something other than 1, change it to 1 now. You’ll want to leave it there until you start to work with unknowns in section IIA. Drag the object to the point labeled 2F on the left end of the ray tool. (You can also move the object with your left and right keyboard keys.) Drag the Screen Position Tool to the same 2F point. Ta da! A nicely focused, upside down cow appears on the frosted glass. An enlarged version also appears in the Image Close-up Screen next to the Object Close-up Screen. Each screen has a grid that can be moved around to make size measurements. Each grid square is 1 cm on a side. Also, try zooming in on the cow object and image on the bench. They should be side-by-side and equal in height. You can right click (Mac: CTRL click) as many as six times to zoom way in. “Show all” will take you back to 100%. You can trade in your cow for a Taj Mahal, a fast red car, or the moon, depending on your mood. The text of this lab generally refers to the cow as the object until the last part of the lab where we’ll trade it in for the Taj Mahal. “Upside-down cow” carries a more serious tone than “upside-down moon.” VPL_Lab -Mirrors-Images 2 Rev 12/19/18 KET Virtual Physics Labs KET © 2019 Procedure I. Plane Mirrors; Virtual and Real Images We’re going to look at the behaviors of our three mirrors to learn the nature of the images they form as well as the geometry behind the image formation. Then we’ll look at the algebraic descriptions of this geometry. We’ll start with the plane mirror. Drag the plane mirror in place on the Ray Optics Tool. It should look something like Figure 4 minus a few added details. The law of reflection states that when a ray of light reflects from a mirror the angle of incidence equals the angle of reflection. The lower, green-colored rays illustrate this. A ray leaves the top of the Object Arrow, strikes the mirror at some point (its midpoint in Figure 4) and then reflects down to the left. The dashed line conveniently helps us see that the angles are indeed equal. Figure 4: Image Formation By a Plane Mirror There are two other ray pairs in Figure 4 that illustrate the same behavior. The orange rays at the top clearly show the same effect. But the purple rays in the middle are less obvious. A ray leaves the top of the object and hits the mirror normally, that is, at a right angle to the mirror. Thus it reflects straight back on itself. The angles of incidence and reflection are both zero in this case. Remember, there are many more rays from the object which hit the mirror. We just need at least two for our work. Behind the mirror (on the right), we see the image. Its height, hi, is clearly equal to that of the object, ho, and with the draggable ruler you can verify that the image is as far behind the mirror, di, as the object is in front, do. This becomes even more obvious when you move the object toward and away from the mirror. (We’ll discuss the way that the light seems to bounce off the back surface of the mirror in the next section.) 1. As you drag the object toward the mirror, picture the equivalent activity of walking toward a bathroom or dressing room mirror. If you walked toward the mirror at 2 m/s, at what speed is your image moving toward the mirror? 2. At what speed is your image moving toward you? Remember, you’re moving too We clearly see our image move toward and away from our body when we move toward and away from a plane mirror. But there’s really nothing there. An image is not something that has any solid reality in the physical world like the object it mimics. If this is so, how can it have a location? To understand the location of images, we first need to understand how we locate actual objects when we look at them. In Figure 5a we’ve added a pair of eyes. These belong to a person, seen from above, who is located between the object and the mirror. That is, you’re looking down on the top of this person’s head. This person is ignoring the mirror for now. Be sure to put yourself in these figures. For the plane mirrors you can actually reenact events by standing in front of a bathroom mirror. Note that the eyes are pointed toward the top of the object so that a different ray from the object enters each eye. Think about it. At any given instant you are actually just looking at one small region of space. For example, you can’t look at a complete sheet of paper. Try it. Your eyes will start madly searching all over it. When you read this sentence you are only looking at a little bit at a time. The rest of it is handled very differently than the part you’re actually focusing on. Consider how much VPL_Lab -Mirrors-Images 3 Rev 12/19/18 KET Virtual Physics Labs KET © 2019 work it would be to actually see all of a brick wall at once and have to keep actively seeing all of it to “keep it there.” We actually see something more like “brickness.” Sorry, I didn’t mean to alarm you. Where were we? The two little eyes were pointed at the top of the object so that they can let the two rays from just that part of the object reach your retina. Most of the time, your eyes are pointed at the same thing. Your eyes can’t look at two different things at the same time. Instead, at a given instant, they both “agree” to focus their attention on one thing, the tip of the Object Arrow in this case. In addition, based on the amount the eyes have to turn relative to straight ahead, we compute the distance to the object and adjust the focus of the eye’s lenses to properly focus the light. Amazing. You probably remember learning to do that by examining your feet when you were lying on your back as a baby. Try it. Look at something far away. Now, focus on something close by. You can feel your muscles straining to turn your eyes away from their relaxed parallel alignment. (A good vacation spot always provides an ample supply of interesting things to look at with relaxed eyes. An ocean, for example!) Again, this is the process of “locating” an object, that is, assigning it a location. Figure 5a: “Locating” an Object Figure 5b: “Locating” an Image Figure 5: “Locating” an Object and an Image In Figure 5b, the person has turned around and is now facing the mirror. Now light is allowed to reflect from the mirror before entering the eyes. (Magically passing through the person’s head.) Note that a different pair of rays, from the many available, is used this time. In Figure 5b, the reflected rays entering the eyes look no different than the direct rays used in Figure 5a. They’re all just rays of light coming from a specific point. The mind does the same triangulation. But this time it notices that your eyes don’t have to point inward so much and concludes that the more parallel rays are coming from a source farther away and behind the mirror. All the information that’s needed for the mind to conjure up an impression of the existence of the object is available. We say that the person is now looking at (locating) an image of the object. When the rays entering the eye are in any way redirected from their straight line path away from the object, we say that the observer is looking at an image. (Even mirages are images.) In this particular case, if you extrapolate back to the apparent source of the light, the image, you find that the rays never passed through that location (behind the mirror). We call this a virtual image. Virtual means “in effect, but not in reality.” Plane mirrors always form virtual images – the image will always be behind the mirror where the light never goes. And since there’s no light present at the image, you can’t form a virtual image on a screen there. You’ll see that our Optical Bench is similarly limited. The Ray Optics Tool will always show where the image is located because it just uses geometry to locate it. But the Optical Bench realistically creates the image using light coming from the object. If no light strikes the screen, no image can be formed on it. Thus the screen can only display real images. Let’s take a closer look at these two types of images. Replace the plane mirror with the converging (concave) mirror. Move the object to the 2F point. Move the Screen Position Tool to the 2F point, which is where the Image Arrow is located. You’ll see the real image on the screen of the Optical Bench and on the Image Close-up Screen. The light is actually hitting the screen and point by point creating the full image. Our Ray Optics Tool just follows a pair of rays from the top-most point on the object. But if you added rays from other points you’d find that they will produce their images at the proper places necessary to build up the full image. Does this mean that you have to have a screen to see a real image? No. VPL_Lab -Mirrors-Images 4 Rev 12/19/18 KET Virtual Physics Labs KET © 2019 Consider Figure 6 with the frosted image screen at the location of the inverted image shown. With the screen in place, the light arriving at the tip of the Image Arrow would be scattered in all directions. Some of this light would travel into the eyes. So the eyes would see light coming from the screen. If the tip of the arrow was pink, the eyes would see pink light coming from that point. Now move the screen away. The light no longer scatters from the image screen. But if you were to put your eyes in the location shown in Figure 6, the rays will continue on into your eyes just as if there was an actual (pink) object at the tip of the inverted image shown. You would then see the virtual image and locate it sort of hanging in space at that point. Figure 6: Seeing an Image Without Using a Screen The images below illustrate a great example of this. In the first image you see a push pin at the bottom of a concave mirror. In the second image you see a second concave mirror with a hole in its center sitting on top of the first one. But this one’s mirrored surfaces faces downward. Note also that it has a circular hole in the top. An image of the push pin and part of the lower mirror is formed by the two mirrors. The image is created at the location of the hole in the top mirror. The push pin appears to be sitting on a mirror at that location. When you study corrective lenses later in this course you’ll learn how they take light from an object at a location where you can’t see things clearly and produce an image of it where you can. For example, if you’re near sighted you may only be able to see things clearly out to 1 meter from your face. Your lenses will take light from a distant mountain and form an image at approximately 1 meter from your eyes! We’ve seen two different types of image – real and virtual. Let’s summarize our key observations about them. REAL VS. VIRTUAL IMAGES: For real images, the light passes through the image and then diverges. We can put a screen at the location of the image and see it displayed there. Or we can allow the light diverging from the image to pass into our eyes which can then form an image (of an image) on our retinas. For virtual images the light only appears to diverge from the image. The light doesn’t actually pass through the image. And as a result a virtual image can never be displayed on a screen. The Nature of an Image Categorizing an image as real or virtual is a part of the process of determining the nature of an image. The nature of an image is determined based on three criteria. To state the nature of the image you’ll pick one from each of the following. a. Is the image real or virtual? b. Is the image reduced in size, the same size, or enlarged in size relative to the object. c. Is the image upright or inverted relative to the object? VPL_Lab -Mirrors-Images 5 Rev 12/19/18 KET Virtual Physics Labs 3. KET © 2019 Record the nature of the image formed by a plane mirror. Choose one for each category. a. □ Real □ Virtual □ No image b. □ Reduced □ Same Size □ Enlarged c. □ Upright □ Inverted As noted earlier, for a plane mirror, the image is as far behind the mirror as the object is in front and the size of the image and object are always the same. One further measurement that will be introduced in more detail soon is the magnification, M. The magnification is the ratio of the image height, hi, over the object height, ho. So for a plane mirror this will always be equal to 1. Figure 7: Object and Image Size and Position for a Plane Mirror II. Concave (Converging) Mirrors 1. The second mirror choice, which you’ve already seen, is a concave mirror. Drag it onto the Ray Optics Tool and then drag the object until the screen looks similar to Figure 8. Figure 8: The Concave (Converging) Mirror 2. Both the object and the image are on the left side of the mirror. Drag the Screen Position Tool all the way to the right. Now start dragging it slowly to the left and watch the screen on the Optical Bench. Drag it just “through” the mirror and stop. 3. Notice what happened on the Image Close-up Screen at the top left of the lab screen. There’s something fuzzy there. That’s a very poor image of a cow. The problem is that it’s not focused because the screen isn’t where the image is located. Drag it a little more and you’ll see the image begin to clear up both on the Close-up Screen and on the Optical Bench screen. Adjust the screen position until the image is well focused. Use the Close-up Screen to make these determinations. 4. What is the nature of this particular image? Check one for each category. a. □ Real □ Virtual □ No image b. □ Reduced □ Same Size □ Enlarged c. □ Upright □ Inverted VPL_Lab -Mirrors-Images 6 Rev 12/19/18 KET Virtual Physics Labs KET © 2019 In the first question asking you to make these choices, you were describing the “nature of the image formed by a plane mirror.” For any plane mirror, there’s exactly one answer for each category. This time the question was not so general. You were asked about “this particular image.” As you’ll soon see, the nature of the image produced by a spherical mirror changes according to the object’s distance from the mirror. We’ll pay a lot of attention to the nature of images in this lab. It’s important. Here’s an example of why it matters. 5. Dentists use mirrors to clearly see what they’re doing when they’re working on your teeth. Would you want your dentist to use a mirror system arranged like the one on your screen now? What would be the advantage of this arrangement? What would be the disadvantage? Look at the Object and Image Close-up Screens. II A. Focal Length, f, Object Distance, do, and Image Distance, di The nature of the images formed by a concave mirror is not as neat and tidy as what we found with plane mirrors. The nature of the image and its location depend on the particular curvature of the mirror and the location of the object relative to the mirror. As shown in Figure 9a, the object distance, do, is the distance from the center of the reflective surface of the mirror out to the object, O. Similarly, the image, I, is located a distance di, from the center of the reflective surface of the mirror. (Just as with plane mirrors we draw the rays and make our distance ...
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Final Answer

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Lenses and Mirrors Lab
This experiment was conducted to attain four objectives. The focus of this lab was on mirrors. These
objectives included;

To familiarize with the nature of the images formed by plane and spherical mirrors.
To learn how to differentiate between real and virtual images.
To identify the relationships among the position of object and image, focal length,
magnification, radius of curvature of plane, converging, and diverging mirrors.
To familiarize with sign conventions, that is, how and why they are used.

As evident from the class lessons, a mention of mirrors and lenses links to how they interact with
light. Reflective and refractive properties of light play a key role in understanding the nature of
lenses and mirrors. The ability of human eyes to perceive light leaving an object and reconstructing a
replica of the object on the retina is important in as far as the topic of optics is concerned. Almost
everyone has had an opportunity to come across a plane mirror and maybe curved mirrors and
lenses. Out of curiosity, one can tell some difference in the way the images are formed.
Plane Mirrors
A plane mirror is a type of mirror whose reflective surface is flat. For a plane mirror, based on the
Law of Reflection, the angle of incidence equals the angle of reflection as illustrated in Figure 1.
According to theory...

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