They were awkward in use, but enabled van Leeuwenhoek to see detailed images. Principal Planes. equation to work! Part 2 Discussion Questions: 1. By carrying out carefully considered practical work, students will enhance their investigative thinking, improve their mastery of techniques and consolidate their understanding of key scientific concepts. be generated by any type of microscope, from a low power stereo at 3X or a transmission electron microscope or scanning probe microscope at 1 X 106 X. Calculate Lens millimeter selection according to area size The Field of View Calculator (or FOV) is used to help predetermine proper lens selection prior to installation. Shop professional, high quality microscopes, microscope accessories, and magnifying lamps. The distance between the objective and eyepiece lenses in a…. findCirclesGrid in Python. Cell Membrane (also known as plasma membrane or plasmalemma) is surrounds all cells. Parts of the Monocular Compound Light Microscope:. With advances in digital cameras and the discovery and development of genetically encoded fluorophores, there has been a huge increase in the use of fluorescence microscopy to quantify spatial and temporal measurements of fluorescent molecules in biological specimens. Everything in the night sky is so far away that it’s not the actual distances between things that we see, it’s the differences in the angle from our vantage point. Determination the approximate field diameter for each of the objective lenses by using ruler Background Information: When viewing a small organism through the microscope, it's usually necessary to have. Other considerations: The working distance is the distance from the bottom of the microscope (lens) to the part of the specimen that is in focus. Surround an area with a perimeter. 7mm 100X -. The magnification for microscope objectives is confusing because to calculate the magnification you must know something about the tube lens that is used along with the objective. INTRODUCTION: The light microscope can extend our ability to see detail by 1000 times, so that we can. A compound microscope has an objective of. A wide selection of laboratory microscopes, compound and stereo microscopes, microscope slides and microscope accessories ideal for laboratories, industrial facilities, clinics, and universities. By Abbey Johnson Bonnell, O. Multiply the two numbers together to find the total magnification of the specimen. findCirclesGrid in Python. cv::undistort. Calculate the magnification of an object placed 6. The working distance is the distance between the objective lens and a sample. Volume is the quantification of the three-dimensional space a substance occupies. •In the data bar of the picture we see: •HFW: The width of the picture. There are Dino-Lite models from zero working distance (touching or close to touching at highest magnifications) and enhanced working distance models for those that require a little space between the microscope and subject and magnification up to 140x. Calculate Lens millimeter selection according to area size The Field of View Calculator (or FOV) is used to help predetermine proper lens selection prior to installation. Record this position as x0. The topic on how to calculate magnification and what units to use, and all the relevant calculations really catch me out. Calculate Magnification of a Compound Light Microscope. The depth of field of a lens is its ability to maintain a desired amount of image quality as the object is positioned closer to and farther from best focus. This is the amount of space you have to work in. Calculating the Diameter of the Field of View One part of our exercise involves the direct measurement of the diameter of the field of view using a clear ruler at 40x and 100x. Calculate the resolving power of a specific lens system if the numerical aperture and wavelength of light is. 1 mm for high-power oil immersion objectives. Angles of elevation or inclination are angles above the horizontal, like looking up from ground level toward the top of a flagpole. Using the Plan Apo 60X oil (N. Great working distance and depth of field are important qualities for this type of microscope. USING THE CALCULATOR. Mechanical stage: A movable platform that holds the slide and brings it up to viewing distance. ) It's much easier if the microscope has an X-Y stage to precisely move the die for each picture. Look more closely. Calculate Magnification of a Compound Light Microscope. Scanning probe microscopy produces images of even greater magnification by measuring feedback from sharp probes that interact with the specimen. This is called bright field microscopy. HOW TO TURN ANY WEBCAM INTO a HIGH POWER MICROSCOPE: Hello friends,this is my first instructable that i made using my old SVB webcam. Objective Working Distance. 2 mm, depending on how good our eyes are. O The ergonomic optical design and construction of the Leica S stereo microscopes are intended to reduce the exertion of the user to a minimum. An understanding of the principles of microscopy shows why light and electron microscopes have been essential in improving our knowledge of cells. Setting up your calibrations. Define the units of length in the 'Unit of Length' field. Note that a specimen is not necessarily placed in the focal plane, e. α: half the opening angle of the objective n: the refractive index of the immersion medium used between the objective and the object (n = 1 for air; n = 1. s by manufacturer as follows:. In other words, this is the minimum distance at which two distinct points of a specimen can still be seen - either by the observer or the microscope camera - as separate entities. That gizmo is a compound light microscope. -makes small adjustments to sharpen the focus that cannot be seen when externally looking at the microscope -can be used to sharpen the focus under 4x, 10x and 40x ***This the only focusing knob that can be used with the high power lens. If the microscope has a fourth objective lens, the magnification will most likely be 100x. Something else important is calculating bullet drop on an optic when you do not have a specific bullet drop compensator built into your rifle. The Microscope has a binocular head, at 30 degree angle for comfortable viewing, and is rotatable 360 degrees for easy sharing of the specimen view. This, if present, is typically the smaller knob on the microscope, and will move the stage a much shorter distance than the coarse focusing knob. Distance traveled is an obvious influencer as it stands to reason that sending something further away is more costly than sending it to a nearby location. You will also learn about magnification, resolution and the parts of the compound microscope. There are two types of light microscope. Collect a power cord from the storage tub. Conversely the lens will have a greater working distance for the same mag. Image-forming light waves pass through the specimen and enter the objective in an inverted cone as illustrated in Figure 1. This page is not intended to give a complete description of how a confocal microscope works and what all the possibilities of its use are. The hand magnifying glass can magnify about 3 to 20×. The largest field of view is 18mm at the longest working distance. Figure 7 shows how to read microscope objective specifications. during dissection). •Start with the base unit and then examine the prefix to determine what to do next. , and Mike Cymbor, O. Notice the field number written on the eyepieces says 18mm. A microscope makes a tiny, nearby object look much bigger. Relative mobility is the distance migrated by a band divided by the distance migrated by the dye front. The distance across the center of the circle is referred to as the diameter of field of view (dFOV). The distance between the real image and the ocular lens (d e) = 6 cm. In addition, the emission spectrum of each microscope was separately measured at intensities of 5% and 100% at a working distance of 20cm. The word stereo comes from the Greek word for solid. • You stay within the working distance of the lens. This image is then viewed with a short focal length eyepiece used as a simple magnifier. The distance between the front edge of the objective lens and the specimen surface (with the surface of the cover glass in case of the cover glass objective lens) when the specimen is focused. and a pencil. You will also use a slightly different type of light microscope called a stereoscopic dissecting microscope. Revised Fall 2018 1 Introduction to the Compound Microscope Cell Structure & Function Laboratory Safety Lab coat, long pants, closed-toe shoes, safety goggles, and nitrile or latex gloves are required. From virtual reality labs to online field trips, innovations in course development help make Ecampus a nationally ranked leader in online education, creating innovative and accessible ways for students to engage with course materials, their classmates and instructors. Verify this. -makes small adjustments to sharpen the focus that cannot be seen when externally looking at the microscope -can be used to sharpen the focus under 4x, 10x and 40x ***This the only focusing knob that can be used with the high power lens. The focal length of the objective lens (f o) = 1. it would be more like a couple of mm, at this point the student is looking at dust and is way out of focus. Window Thickness Calculator. Wholesale and dealer pricing available on Surgitel Loupes Work Distance Adjustment Caps 100. Example: The Meade DS-2070AT telescope has an objective lens focal length of 700mm; when this telescope is used with a 25mm eyepiece, a power of 700/25 = 28 power (written as "28x") results. The working distance decreases as the NA and magni cation both increase. The fully coated optical system produces sharp and clear images with extremely good flatness and contrast over the complete viewing area. Different area areas have an influence on the count of the positive rate under the microscope. it means at which distance u able to see the object clearly,,,,, even at that distance u can draw the object image on paper at same time. The l0X objective (low power) has a working distance (the distance from lens to object when the object is in focus) of about 4 mm. That gizmo pictured to the left is a BIG deal. Microscope magnification calculation examples: When the ocular lens is 10× and the objective lens is 10×, the field of view is 800 µm. This will reduce the resolution. With lenses that focus internally, or zoom lenses, the simple formula above is insufficient to allow you to calculate exactly what your minimum focusing distance and magnification can be for any given lens, focal length, and extension. Most microscope objective specifications are listed on the body of the objective itself: the objective design/standard, magnification, numerical aperture, working distance, lens to image distance, and cover slip thickness correction. during dissection). Find the Speed of a Protist Joshua Segaloff Summary This lesson is part of a whole week unit on comparing single celled organisms to multi-celled organisms using a microscope. 00 D to +48. The most familiar type of microscope is the optical, or light, microscope, in which glass lenses are used to form the image. 2 Responses to “Salt and Sugar Under the Microscope” Sydney Capodano November 21st, 2011 at 11:18 pm. Place the microscope on a table or bench which is stable and free from vibrations. a= f´* ( y / y´ +1) Note: Even when using the drop-down lists own values can be entered. Right working distance between eye & nosepiece. Gastric retention devices based on super-porous IPN hydrogels (SPIHs) with the improved me-chanical properties are expected to withstand compres-sion pressure and mechanical frictions in the stomach better than the control SPHs. Originally, I used the same scale for magnified and unmagnified, which made it easy to calculate the magnification. 20 mm from a compound microscope that has a 6. With advances in digital cameras and the discovery and development of genetically encoded fluorophores, there has been a huge increase in the use of fluorescence microscopy to quantify spatial and temporal measurements of fluorescent molecules in biological specimens. findCirclesGrid in Python. In other words, this is the minimum distance at which two distinct points of a specimen can still be seen - either by the observer or the microscope camera - as separate entities. The actual value is operator and instrument dependant. Just enter the focal length of your lens, distance to your subject and selected f-stop, and see what happens. The ocular micrometer may now be used to measure objects magnified by the microscope. The smallest interval on the scale represents a specific distance. and by comparing the beam's appearance before and after it passes, the microscope can calculate the distortion and correct it. Description. To calculate total magnification, find the magnification of both the eyepiece and the objective lenses. Place the microscope on a table or bench which is stable and free from vibrations. So, starting with the electron that travels at 10% of the speed of light. Working distance is generally described as the distance between the workpiece and the objective lens of the microscope when the object being examined. How to Calculate Microscope Field of View To calculate the field of view of microscope you need to know the eyepiece magnification, field number and objective lens. A person with a normal near point (25cm) using a compound microscope with objective of focal length 8. 0 mm 60x 4 3. Biology 3A Laboratory Lab 3: Microscopes and Cells OBJECTIVE • To learn the proper use and care of compound microscopes. Working Distance (W. Calculate the focal distance of a microscope: 1. How to Calculate Depreciation Posted on July 10, 2009 by dGuru With all of the rules and regulations governing depreciation, and the various methods of depreciation, one may find it difficult to actually calculate depreciation. a decrease in the depth of field d. Here is an easy to use calculator for these questions. Not to be confused with magnification, microscope resolution is the shortest distance between two separate points in a microscope's field of view that can still be distinguished as distinct entities. Thus, the total magnification in a compound microscope is a function of the objective magnification multiplied by the eyepiece magnification. As the same sample may look to be different sizes under different magnifications, the Graticule must be calibrated. Resting place for slides. findCirclesGrid NOT Working. Increasing the magnification and the numerical aperture of the objective reduces the working distance, i. The hand magnifying glass can magnify about 3 to 20×. Please try to avoid jargon; I don't really understand big terms, but there must be a simple way of working all this out. 4x) is clicked into position. 56, p 930). Once these calculations are made, the class data is combined and students graph magnification power as a function of lens diameter from combined class data. just place anything 1. For this and subsequent work on the subject, he was awarded the Nobel Prize for Physics in 1986. 25mm at Boli Optics Microscope Store. Figure 7 shows how to read microscope objective specifications. calculate length, area, and volume using the SI base unit for length and units derived from that base unit. Reasonable depth of field: our microscope makes it quite clear to see no matter how complicated the structure of object is. Helmenstine holds a Ph. 5 mm 2 cm 200 µm 1 cm 40 µm 2 cm 100 µm 200X 5 cm 100X 4 cm 50X 2. Dissecting Microscopes on the other hand have a low final magnification but are useful when a large working distance between the objectives and the stage is required (e. Image-forming light waves pass through the specimen and enter the objective in an inverted cone as illustrated in Figure 1. In working with lenses, there are three important quantities to consider: The object distance s is the distance along the axis of the lens to the object. Working distance determines how far to position an imaging lens from the object under inspection. The transmission electron microscope (TEM) and scanning electron microscope (SEM) are two common forms. calculate the diameter of the field and the total magnification for both low – and high – power lens systems. For the solar system we use the Earth-Sun distance. Be able to calculate the total magnification of your microscope. Of course, there are some details about which we must be concerned. A practical guide for fluorescent confocal microscopy by Dirk Bucher. LAB 3 – Use of the Microscope Introduction In this laboratory you will be learning how to use one of the most important tools in biology – the compound light microscope – to view a variety of specimens. s by manufacturer as follows:. These microscopes have two eyepieces and two objective lens using separate optical paths. Microscopy is the use of a microscope to view small- scale structures and organisms. Where the magnification of the objective is Mo and the eyepiece magnification is Me. 1 mm for high-power oil immersion objectives. The 40X objective (high power) has a working distance of about l mm. The distance between the objective lens and the ocular lens of the microscope. Part 1: Estimating Size of Specimens Under the Microscope a. The numerical aperture of a microscope objective is a measure of its ability to gather light and resolve fine specimen detail at a fixed object distance. Open the movable arm of the clip and place the slide between the clips. Step by step procedure for the use of the microscope. The focal distance should also not be confused with the working distance, which is the distance between a specimen and the lens housing. Magnification Calculations. Open Peer Review Any reports and responses or comments on the article can be found at the end of the article. As you work, be sure to record the unusual patterns of asci. This occurs to a (far) lesser extent whenever I use it for a shorter time. Place the glass slab of least thickness over the mark P. Hooke's Law Calculator Inelastic Collision Calculator Khudsen Number Calculator Kinetic Friction Calculator Stokes Law Calculator Torricelli's Theorem Calculator Velocity Acceleration Time Calculator Volume Flow Rate Calculator Wavelength Frequency Calculator Weber Number Calculator Work Force Distance Calculator Young's Modulus Calculator. Lens Size The lens size is the optical area of the lens, generally measured in diameters for round lenses or in length and width for rectangular or square lenses. • Prepare a wet mount, determine the magnification and size of the field of view, and determine the depth of field. Great use! Thank you! I personally use a stereoscopic Microscope with 5x Magnification (up to 40x…) designed for biology and watch making. and a pencil. describe how the slide of the letter e provides information on the inversion of the image in the compound light microscope. Update: Also, an object is 3. Reasonable care must be taken in handling and use to protect surfaces from scratches, abrasions, pits or digs that can act as break sources. In other words, this is the minimum distance at which two distinct points of a specimen can still be seen - either by the observer or the microscope camera - as separate entities. How to determine the measurement of the diameter of your field of view when using a microscope. Known : The distance between object and the objective lens (d o) = 2 cm. The term in general is called the -number and is used to denote the light per unit area reaching the image plane. Measuring Relative Mobility of Protein Bands. Record this position as x0. making an electron microscope has been stirring around in the back of my mind for a few years now. History of the Microscope - What is a microscope? First a definition. Setting up your calibrations. CAUTION - Some microscopes have a viewing head with an adjustable interpupillary distance which changes the tube length of the microscope. lenses magnifications of 3X to 20X are possible with 6. So a confocal microscope has slightly better resolution horizontally, as well as vertically. Magnification of the Telescope Theory Size and Distance in the Sky. Relative mobility is the distance migrated by a band divided by the distance migrated by the dye front. There are other types of microscope that use more exotic means to generate contrast, such as phase contrast, dark field, differential interference contrast. Van Leeuwenhoek's home-made microscopes were very small simple instruments, with a single, yet strong lens. A) General care of the compound microscope 1. Description. lenses magnifications of 3X to 20X are possible with 6. There is a cool bacterium you want to study in closer detail so you want to build a microscope to see it. For more distant objects we use the speed of light. Resolution is not magnification. To check if this device will work, you decide to calculate the distance from the circle that the ion goes before it stops. findCirclesGrid in Python. Measuring Distance Between Points. Show your work in the space below (remember to include units as necessary). Microscopes. In order to calculate the depth of field, one needs to first decide on what will be considered acceptably sharp. How to Calculate Depreciation Posted on July 10, 2009 by dGuru With all of the rules and regulations governing depreciation, and the various methods of depreciation, one may find it difficult to actually calculate depreciation. That gizmo pictured to the left is a BIG deal. One of the most common occurs when a valve-like mechanism between the bladder and ureter (urine tube) fails to work properly and allows urine to back up (reflux) to the kidneys, causing infections and possible kidney damage. A microscope should not be focused by moving the objectives and the slide closer together because it will affect the working distance. These microscopes have two eyepieces and two objective lens using separate optical paths. Microscope Books There are amazing, hidden worlds everywhere - places you can only visit with a microscope. The new focal plane is digitized and stored. camera calibration depth coverage. Working distance can range from 50 mm for dissecting or stereo microscope objectives to less than 0. 4m and an eyepiece of. Gently release the arm. So if I look at the front of an 8-inch scope where it says "D=203mm", I know the maximum magnification is 203. Maximum working distance is 5m under WiFi mode Can be connected to multiple iPads or computers at the same time under WiFi mode Can take pictures and videos Supplied with software WiFi DIGITAL MEASURING MICROSCOPE CODE ISM-WF200* View field 8. The distance from the center of the lens to this point is the focal length. Measure PD your self. Since the working distance (WD) also increases to match the longer objective focal length, manufacturers who use a parfocal distance of 45mm are at a disadvantage in their inability to utilize the longer working distance by Nikon. If the microscope has a fourth objective lens, the magnification will most likely be 100x. Lens Size The lens size is the optical area of the lens, generally measured in diameters for round lenses or in length and width for rectangular or square lenses. Here it says that the actual distance on the specimen is 0. I wrote a brief discussion here of the difference between resolution and magnification. lenses magnifications of 3X to 20X are possible with 6. The numerical aperture of a microscope objective is the measure of its ability to gather light and to resolve fine specimen detail while working at a fixed object (or specimen) distance. This image is then viewed with a short focal length eyepiece used as a simple magnifier. The focal length of the ocular lens (f e) = 6 cm. 20 mm from a compound microscope that has a 6. 9TAREEN PIR MEHR ALI SHAH ARID AGRICULTURE UNIVERSITY 10. Working of Scanning Tunneling Microscope. The laser beam is considered to be dangerous if viewed from a closer distance than that. The calculator should in no way be interpreted as a guarantee. 3D Imaging 3D DISPLAY FUNCTION When observing the surface of an object with a microscope, it can be very difficult to determine the shape or topography of the surface since only a small area can be in focus at one time. a) compare the structure of typical animal and plant cells by making temporary preparations of live material and using photomicrographs. Like FOV, depth of field also declines as magnification increases. it means at which distance u able to see the object clearly,,,,, even at that distance u can draw the object image on paper at same time. Microscope objectives are generally designed with a short free working distance, which is defined as the distance from the front lens element of the objective to the closest surface of the coverslip when the specimen is in sharp focus. Can be turned to change objectives/magnif. Be aware of this change in working distance with increasing magnification so as to prevent damage to your specimens. The distance between the real image and the ocular lens (d e) = 6 cm. Depth of field is the distance between the nearest and farthest points in a sample that appear sharp in the viewed image. It decreases as magnification, resolution and numerical aperture increase. What are the magnifications of the eyepiece and objective? What is(are) the numerical aperture(s)? What is the total magnification? What is the working distance (at which distance from the objective lens is the image in focus?) How would you calculate the focal length of each lens?. This distance is the resolution or resolving power of our eyes. Each Nikon microscope objective is precision-crafted to provide the highest level of clarity and overall optical performance. As you increase the magnification the working distance decreases dramatically. The most familiar type of microscope is the optical, or light, microscope, in which glass lenses are used to form the image. The distance within which objects can be seen clearly (i. BRESSER Science IVM 401 Microscope At the BRESSER Science IVM 401, the usual direction of illumination and observation is inverted: One illuminates the sample from above and observes it from below. The magnification of the objective depends on the distance (d) between the eyepiece and the focal plane and on its focal length (fo. working distance (WD) 1. In previous scanning quantum dot microscopy work, however, we had to move to an individual site on the sample, measure a spectrum, move to the next site, measure another spectrum, and so on, in. Calculate the resolving power of a specific lens system if the numerical aperture and wavelength of light is. Modern microscopes are precision instruments and should be treated as such. So the image, when seen with the eyepiece only, has a diameter or 20 mm. Something else important is calculating bullet drop on an optic when you do not have a specific bullet drop compensator built into your rifle. If you have a DIN microscope objective (160mm tube length, not infinity corrected), then the focal length is given by the following: flange - object distance = 45 mm flange - image distance = 150. what is meant by the working distance of a microscope. All's you need is a ruler, graph paper. Turn the revolving turret (2) so that the lowest power objective lens (eg. Modern light microscopes can magnify images about 1500 times, while electron microscopes can magnify images about two million times. The diagram shows the microscope in normal adjustment, that is, with the final image at the near point (25 cm from the eye) (distance D from the eye lens). As you increase the magnification the working distance decreases dramatically. findCirclesGrid NOT Working. Part 1: Estimating Size of Specimens Under the Microscope a. Length SI is a decimal system. calculate the diameter of the field and the total magnification for both low – and high – power lens systems. Understand and be able to name the differences between a compound and a dissecting microscope. Download the image to your Week 2 folder and use the techniques you learned here to set a scale for the image. On either side, the electrons are present up to the Fermi energy. To practice calculating magnification, copy the following chart into your lab report and in the table. Dino-Lite Long Working Distance For tasks where extra distance to the object and a larger field of view is required Dino-Lite offers a series of Long Working Distance microscopes. The parts of a typical instrument are shown in Fig. Working distance must also be taken into consideration when choosing a microscope, as it is extremely important to be comfortable when working under the microscope for prolonged periods of time. 3m focal length. G-Pen F610 is the brand new slim tablet with 6-Inch x 10-Inch working area and one cordless pen for PC Windows and MACs to ite, draw, sketch and sign emails. This is a small, transparent ruler that is superimposed over the image. NOHD is the abbreviation of "Nominal Ocular Hazard Distance". Everything in the night sky is so far away that it’s not the actual distances between things that we see, it’s the differences in the angle from our vantage point. So if I look at the front of an 8-inch scope where it says "D=203mm", I know the maximum magnification is 203. observe slides under the microscope 3. Examine the letter ‘e’ slide. com FREE DELIVERY possible on eligible purchases. Q&A > Biology > looking at a cell under a microscope, you note that it is prokaryote. distance vision See distance vision. In 1986, Binnig and Quate demonstrated for the first time the ideas of AFM, which used an ultra-small probe tip at the end of a cantilever (Phys. The Magnification Equation for a Microscope. name the parts of a microscope 2. #c = 3 * 10^(8)"m/s "#, which means that the electron's speed will be. This produces a stereo or 3-dimensional image of the specimen. Prepared Microscope slides: Letter ‘e’ Wet Mount: Pond or creek water samples Honeybee head in plastic Pennies (2-3) Wood sample 2. Math: Young students count the number of specimens viewed on a slide, calculate magnification power, and learn about the metric system (e. VIBRATION ISOLATION 12. Resolution is not magnification. KEYENCE America. With its angled view, eye distance adjustment and dioptre compensation, the Krüss MBL 2000 is comfortable to work with and reduces eye fatigue. Chapter 3: The Microscope Objectives: Know the parts of the microscope and their function Be able to calculate total magnification and working distance Understand how to perceive depth base substage light stage condenser iris diaphragm lever coarse adjustment knob fine adjustment knob head arm ocular (eyepiece) nosepiece objective lenses. The diagram shows the microscope in normal adjustment, that is, with the final image at the near point (25 cm from the eye) (distance D from the eye lens). different objectives are moved into position, giving parfocality. To work out the size of an object viewed with a microscope, a Graticule is used. Find the Speed of a Protist Joshua Segaloff Summary This lesson is part of a whole week unit on comparing single celled organisms to multi-celled organisms using a microscope. They will learn how to place slides on the tray, use the focus, and magnifications. In 1675, Anton van Leeuwenhoek brought the microscope to the attention of biologists. • Using a microscope identify a protist • Pairs then design a method for calculating the speed of a protist • Students then will fill out the worksheet to be handed in Assessment The teacher walks around the class and makes sure that all students are engaged and on task. How does a Galilean telescope work? The Galilean telescope was innovative in that he was the first to expand the range of magnification of the new spyglasses beyond 3X, using his particular set of lenses. The image will look something like the following with a high power objective: This process should be repeated with each objective. Description. Working distance determines how far to position an imaging lens from the object under inspection. The magnification for microscope objectives is confusing because to calculate the magnification you must know something about the tube lens that is used along with the objective. all of the above 13.