Biology Magnification Questions And Answers Pdf? Top Answer Update

(Adapted from http://www.biologycorner.com/)

Introduction: A microscope is an instrument that enlarges an object so that it can be seen by the viewer. Because cells are usually too small to see with the naked eye, a microscope is an indispensable tool in the field of biology. In addition to magnification, microscopes also provide resolution; H. the ability to distinguish two nearby objects as separate. A combination of magnification and resolution is necessary to see specimens clearly under the microscope. The light microscope uses a series of lenses to direct a beam of light onto the sample to provide the viewer with a clear image of the sample. Parts of the microscope are checked in this laboratory. The students learn how to use and care for the microscope properly and observe samples from pond water.

Parts of the microscope:

Magnification: Your microscope has 4 objective lenses: Scanning (4x), Low (10x), High (40x) and Oil Immersion (100x). In this exercise, you will not use the oil immersion objective; It is for viewing microorganisms and requires technical instructions that are not covered in this procedure. In addition to the objective lenses, the ocular lens (eyepiece) has magnification. The total magnification is obtained by multiplying the magnification of the eyepiece and objective. Magnification Eyepiece Lens Total Magnification Scanning 4x 10x 40x Low Power 10x 10x 100x High Power 40x 10x 400x Oil Immersion 100x 10x 1000x

General Procedures: 1. Ensure all backpacks, purses, etc. are removed from the table top. 2. Carry the microscope by the base and arm with both hands. 3. Store with the cable wrapped around the microscope and the scan lens engaged.

To focus samples: 1. Connect power to your microscope and turn on the illumination. 2. Always start with the table as low as possible and use the scanning lens (4x). Chances are you can see something in this shot (sometimes it’s just one color). Use the coarse adjustment knob to focus: the image may be small at this magnification, but you won’t be able to find it at higher magnifications without this first step. Move the cross stage until your focused image is also centered. 3. Once you have focused with the scan lens, switch to the low power lens (10x). Use the coarse knob to refocus and move the cross stage to re-center your image. Again, if you haven’t focused on this level, you won’t be able to get to the next level. 4. Now switch to the high power objective (40x). At this point, use ONLY the fine adjustment knob to focus the samples. 5. If the sample is too light or too dark, try adjusting the aperture.

Cleaning: 1. Store the microscope with the scanning lens in place and the stage in its lowest position. 2. Wrap the cable around the microscope. 3. Place the slides back in the original slide tray.

Troubleshooting: Occasionally you may encounter problems when working with your microscope. Here are some common problems and solutions. 1st picture is too dark! Adjust the aperture, make sure your light is on. 2. There is a blob in my field of view – even if I move the slider, the blob stays in the same place! Your lens is dirty. Use lens paper and only lens paper to thoroughly clean the objective and eyepiece lens. The eyepiece lens can be removed to clean the inside. 3. I can’t see anything at high power! Remember the steps: if you can’t focus when you scan, and then at low power, you can’t focus at high power. 4. Only half of my field of vision is lit, it looks like there’s a crescent moon in there! You probably haven’t fully locked into your aim. 5. I see my eyelashes! You are too close to the targets. Tilt your head back a little. 6. This is giving me a headache! Relax. Try adjusting the eye relief, check that the intensity of your light isn’t too high or too low. Take breaks if necessary! Note Be patient and keep trying. Using a microscope takes practice!

Part 1: Alignment of Images in the Microscope A big part of learning microscopy is getting used to the alignment of images viewed through the eyepiece as opposed to the naked eye. A common mistake is moving the stage in the wrong direction to find the sample. This procedure is for practice only and is intended to make the microscope easier for new users to use. Materials: Compound microscope

Slide with the letter “e” Procedure: 1. Place the slide with the letter “e” on the mechanical stage. Be sure to note the orientation of the letter “e” as it appears to the naked eye. 2. Use the SCANNING (4x) lens and coarse focus setting to focus, then move the XY stage around to find the letter “e”. Note the orientation when looking through the eyepieces. Does the lens of the microscope reverse the image? _________ Does it mirror the image? (upside down) _________

Part 2: Practice Microscope Depth of Field This part of the procedure is another exercise to demonstrate depth perception. Many new microscope users find it difficult to imagine that the sample on the slide is three-dimensional. As the stage moves up and down, different threads will be in focus. Materials: Compound microscope

Microscope slide with 3 threads Procedure: 1. Place the thread slide on the mechanical stage. 2. Use the SCANNING (4x) lens and coarse focus setting to focus, then move the cross stage around to find the threads. 3. If necessary, switch to the low magnification objective (10x) and refocus. 4. Determine which thread is on the bottom, middle, and top of the slide. Top middle bottom

Part 3: Examination of pond water & microorganisms Materials: Compound microscope

Microscope slide

coverslip

transfer eyedropper

Pond water sample Procedure: 1. Transfer a drop of pond water onto a slide using the transfer pipette. The best specimens usually come from below and are likely to contain chunks of algae or other debris that you can see with the naked eye. 2. Place the coverslip on the slide. 3. Focus the lens on SCAN (4x), then move the mechanical stage to scan the slide for viable microorganisms. They look for tiny floating creatures – they can look green or clear and they can be very small. Pick one to focus on and center it in your field of view. Note You may want to use the ProtoSlo to prevent your organisms from swimming too fast! 4. Switch to low power (10x). This may be enough to show your selected organism. Try to notice how it moves and do your best to draw it as you see it, unless you need a higher magnification. 5. Once you have centered and focused the image, switch to high power (40x) and refocus. Note movements and draw the organism as you see it. Note Remember NOT to use the coarse adjustment knob at this time!

How to estimate size under a microscope

| K-12

Measuring things under a microscope at low magnification is not difficult if you are willing to work with estimates and accept approximations. Estimating to a higher power requires some math, but you can accomplish this with a simple division formula and a drawing to scale of the object being measured.

Estimate size under the microscope

1 Start by sizing the field of view of the microscope at 40x magnification.

2 Place the clear ruler in the line of sight; It measures the field of view at around 4 to 5 millimeters.

Adjusted to low power 3 100 times, it can be estimated at about 2 to 3 millimeters. Convert this measurement to microns; the view at 100x magnification can be estimated at 2,000 to 3,000 microns. You can estimate anything you want to measure in this low-power area – depending on how much of the field it covers – by holding the ruler as a measurement grid on the left side of the image.

4 Make a scale drawing to help you make more detailed estimates at higher power. Draw a circle on paper with a compass; this represents the field of view. Draw to scale the observed object, e.g. B. a single cell from an array of cells.

5 Note the magnification, the diameter of the circle/field of view, the number of cells spanning that diameter, and finally the estimated length of a cell. Finding the length of that one cell is the goal of your measurement exercise.

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Kathryn has been teaching math in high schools and universities for over 10 years. She has a Ph.D. in Applied Mathematics from the University of Wisconsin-Milwaukee, an M.S. in mathematics from Florida State University and a BS. in mathematics from the University of Wisconsin-Madison.

How to calculate the magnification of a concave mirror

Step 1: Identify both the distance between the object and the mirror, {eq}d_o {/eq}, and the distance between the image and the mirror, {eq}d_i {/eq}, or both identify the height of the object, {eq}h_o {/eq}, and the height of the image, {eq}h_i {/eq}.

Sign conventions: distances in front of the mirror are negative, distances behind the mirror are positive, upright images have positive height, and inverted images have negative height.

Step 2: Substitute the values ​​determined in step 1 into the magnification equation {eq}M = \dfrac{h_i}{h_o} = – \dfrac{d_i}{d_o} {/eq}

What is a concave mirror and the magnification equation?

Concave Mirror: A concave mirror is a curved mirror that curves away from the light source.

Magnification Equation: The magnification equation for a mirror is {eq}M = \dfrac{h_i}{h_o} = – \dfrac{d_i}{d_o} {/eq}, where {eq}h_i {/eq} and {eq }h_o {/eq} are the heights of the image or object and {eq}d_i {/eq} and {eq}d_o {/eq} are the distances between the mirror and the image or object. If {eq}|M| < 1 {/eq}, the image is smaller than the object and if {eq}|M|>1 {/eq}, the image is larger than the object. If the magnification is positive then the image is virtual and if the magnification is negative then the image is real.

We will use these steps, definitions and equations to calculate the magnification of a concave mirror in the following two examples.

Example of calculating the magnification of a concave mirror – virtual image

If a bottle is placed 9 cm in front of a concave mirror and its image appears to be 6 cm behind the mirror, what is the magnification of the mirror rounded to two decimal places?

Step 1: Identify both the distance between the object and the mirror, {eq}d_o {/eq}, and the distance between the image and the mirror, {eq}d_i {/eq}, or both identify the height of the object, {eq}h_o {/eq}, and the height of the image, {eq}h_i {/eq}.

Sign conventions: distances in front of the mirror are negative, distances behind the mirror are positive, upright images have positive height, and inverted images have negative height.

We get the distance between the object and the mirror and the distance between the image and the mirror. Since the object is in front of the mirror, the distance is considered negative. Since the image is behind the mirror, the distance is considered positive. Because of this,

{eq}d_o = -9 {/eq} cm

{eq}d_i = 6 {/eq} cm

Step 2: Substitute the values ​​determined in step 1 into the magnification equation {eq}M = \dfrac{h_i}{h_o} = – \dfrac{d_i}{d_o} {/eq}

Substituting the values ​​from step 1 into the magnification equation {eq}M = -\dfrac{d_i}{d_o} {/eq} we get:

{eq}M = – \dfrac{d_i}{d_o}\\ \\ M ={\rm -\dfrac{6\ cm}{-9\ cm}}\\ \\ M = {\rm \dfrac{ 2\cm}{3\cm}}\\ \\ M \approx. 0.67 {/eq}

The magnification is about {eq}0.67 {/eq}, which means the image is smaller than the object (since {eq}|0.67|<1 {/eq}) and the image is virtual (since {eq}0.67 {/eq} is positive). Example of calculating the magnification of a concave mirror - real image If a stone 4mm high is placed in front of a concave mirror and its inverted image is 3mm high, what is the magnification of the mirror rounded to two decimal places? Step 1: Identify both the distance between the object and the mirror, {eq}d_o {/eq}, and the distance between the image and the mirror, {eq}d_i {/eq}, or both identify the height of the object, {eq}h_o {/eq}, and the height of the image, {eq}h_i {/eq}. Sign conventions: distances in front of the mirror are negative, distances behind the mirror are positive, upright images have positive height, and inverted images have negative height. We get the heights of the object and the image. The image is inverted so its height is negative. Because of this, {eq}h_o = 4 {/eq}mm {eq}h_i = -3 {/eq}mm Step 2: Substitute the values ​​determined in step 1 into the magnification equation {eq}M = \dfrac{h_i}{h_o} = - \dfrac{d_i}{d_o} {/eq} Substituting the values ​​from step 1 into the magnification equation {eq}M = \dfrac{h_i}{h_o} {/eq} we get: {eq}M = \dfrac{h_i}{h_o}\\ \\ M = {\rm \dfrac{-3\ mm }{4\ mm}}\\ \\ M = -0.75 {/eq} The magnification is {eq}-0.75{/eq}, which means the picture is smaller than the object and the picture is real.

Most compound microscopes come with interchangeable lenses known as objective lenses. Objectives come in a variety of magnification powers, the most common being 4x, 10x, 40x and 100x, also known as scanning, low power, high power and (typically) oil immersion objectives respectively. Let’s take a closer look at the different magnifications of lenses and when you would use them.

Scan lens (4x)

A scan lens offers the lowest magnification performance of any lens. 4x is a common magnification for scanning lenses, and when combined with the magnification power of a 10x eyepiece, a 4x scanning lens gives a total magnification of 40x. The name “scanning” lenses comes from the fact that they give the viewer about enough magnification for a good overview of the slide, essentially a “scan” of the slide. Some targets with even lower performance are discussed below under Special Targets.

Low power lens (10x)

The low-power lens has greater magnification power than the scanning lens and is one of the most useful lenses when it comes to observing and analyzing slide samples. The total magnification of a low power lens combined with a 10x eyepiece is 100x magnification, allowing you to view the slide closer than a scanning lens without getting too close for general viewing purposes.

Figure 1. Sample lens magnifications.

High performance lens (40x)

The powerful objective lens (also called “high dry” lens) is ideal for observing fine details in a sample. The total magnification of a high performance objective combined with a 10x eyepiece is equivalent to 400x magnification, giving you a very detailed image of the sample on your slide.

Oil immersion objective (100x)

The oil immersion objective offers the highest magnification with a whopping 1000x total magnification in combination with a 10x eyepiece. But the refractive index of air and your slide is slightly different, so a special immersion oil needs to be used to bridge the gap. Without a drop of immersion oil, the oil immersion objective will not work properly, the object will appear blurry, and you will not get optimal magnification or resolution. Oil immersion objectives are also available from some manufacturers at lower magnifications and offer higher resolution than their “high dry” counterparts.

Special lenses (2x, 50x oil, 60x and 100x dry)

Several other objective lens magnifications are available that are useful for specific applications. The 2x objective, which is widely used in pathology, has only half the magnification of a 4x scanning objective and thus offers a better overview of the sample on the slide. The 50x oil immersion objective, often used in place of the 40x objective, is used as the gold standard for blood smear observation. Often available in either dry or oil immersion, the 60x objective offers 50% more magnification than a 40x objective. The 60X dry objective is sometimes chosen over a 100X oil immersion objective for higher magnification without the need to use oil immersion. Finally, the 100x dry objective does not require immersion oil to achieve high magnification (still 1000x when paired with 10x eyepieces). However, the numerical aperture (a measure of an objective’s resolving power) of a 100x dry objective is much lower than that of a 100x oil immersion objective, and consequently the objective’s ability to resolve fine detail in the sample is also much lower.

immersion media and lenses

It is important to always use the correct immersion media (e.g. air, water, oil, etc.) dictated by your lens.

The image produced by the wrong immersion media is blurry. In general, lenses are designed to “look” through an immersion medium with a specific index of refraction (a topic for another article). For example, air has a refractive index close to 1.0, while standard immersion oil has a refractive index of ~1.51.

You can damage the lens if you use the wrong immersion oil.

If you are interested in purchasing different types of objective lenses for your microscope in classroom, laboratory, research facility or other purpose, ACCU-SCOPE can supply the products you are looking for. Contact us today to learn more about our objectives and other microscope accessories.

Answers to frequently asked questions about microscopes

All beginners usually face some difficulties when they start working with a microscope. So if you’ve recently bought a microscope, you most likely have some reasonable and perfectly understandable questions. What magnification do I need? Does the field of view play an important role? Why do I need additional eyepieces? We’ve collected answers to the most frequently asked questions to help you clarify. This information will be useful not only for those who already own a microscope, but also for those who are just planning to buy this optical instrument.

“Why is it important to start observing at 4x magnification?”

A typical compound optical microscope has three or four objective lenses with 4X, 10X, 40X, and 100X (oil immersion) magnifications. The 4x objective offers the lowest magnification, allowing you to observe a large area of ​​the sample. This way you can easily find the desired area for further microscopic observation. Once you find the area, place it in the center of the field of view and switch to a higher magnification lens. It is much easier to focus the view with a low magnification lens than with a powerful one.

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“How do you use a microscope as a measuring tool?”

You can measure the size of a sample using a microscope, but first the microscope must be calibrated. This requires a micrometer scale (known as a crosshair) integrated in the eyepiece of the microscope and a measuring scale on the object stage. The reticle has graduations, but you cannot use them to measure the samples directly. Let’s assume a stage scale has a scale value of 0.01 mm. If you align the scale on the table with the eyepiece scale, you will see that the X divisions on the eyepiece scale correspond to the Y divisions of the measurement scale on the table. The following formula is used to calculate the division value of the eyepiece scale:

Eyepiece division value = 0.01 * Y/X

Calculations like this need to be done for every possible combination of eyepieces and objectives as they give different magnifications.

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“How to Calculate the Magnification of a Microscope”

To calculate the magnification of a microscope, simply multiply the magnification of the microscope eyepiece by the magnification of the objective lens. The total magnification of a typical compound microscope with a 10x eyepiece and 4x, 10x, 40x, 100x objectives is 40x, 100x, 400x, and 1000x depending on the lenses used. The same principle applies to stereo microscopes. Some stereo microscopes are equipped with objectives that have a variable magnification ranging from 0.75x – 7.5x. The overall magnification of the microscope with a 10x eyepiece varies accordingly between 7.5x and 75x; with a 25x eyepiece – from 18.75 to 187.5x.

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“How is the magnification of a microscope related to the focal length?”

In microscopy, focal length is the distance between the objective lens and the top of the object being viewed. The focal length of the optical system shows how efficiently the system collects and focuses light rays. Usually, the greater the magnification of the microscope, the shorter the focal length.

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“How do you take photos through a microscope?”

There are several ways to take photos with a microscope. Many modern microscopes are equipped with built-in digital cameras that are connected to a PC via a USB cable. It is very convenient to take pictures with such microscope models. Even if your microscope doesn’t have a built-in digital camera, you still have the option to take photos. There are a large number of microscope camera models that can be installed in place of an eyepiece. With a special adapter you can also connect a compact camera or even a DSLR camera to your microscope. Compact cameras are mounted in such a way that their lens “looks” into the eyepiece of the microscope. DSLR cameras work by replacing the camera’s lens with an eyepiece tube adapter.

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“What is the difference between low and high power microscopes?”

This question is a bit tricky as the definitions are a bit blurry. For example, optical (light) microscopes are usually equipped with four objectives: 4x and 10x are low magnification objectives; 40x and 100õ are powerful. The overall magnification (obtained with a 10x eyepiece) of less than 400x characterizes the microscope as a low-performance model; more than 400x as strong. Because a typical compound microscope offers greater magnification than a stereo (or dissecting) microscope, some sources refer to stereo models as part of the low-power microscope group and compound microscopes as high-power models.

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“We are looking for a teaching microscope. Is it better to go for a three or four lens model?”

It depends on the purpose of your observation. Basic teaching microscopes usually come with three objective lenses (4x, 10x and 40x). The maximum magnification power of these models is 400x. The advanced teaching microscope models are usually equipped with the fourth objective – 100x oil immersion objective. When using this objective with a 10x eyepiece and oil immersion technique, you can achieve 1000x magnification. With the 1000x magnification, you can observe the target object in great detail. However, such a large increase can cause some difficulty in focusing on objects. The oil immersion technique is required (which can be a tedious task), plus the lens itself is a fairly expensive accessory. At 400x magnification, you won’t get as detailed an image as at 1000x, but it’s much easier to focus on objects, there’s no need to use immersion oil, and you’ll save more money too.

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“What is diopter compensation?”

Diopter adjustment allows you to focus one eyepiece independently from the other to compensate for the difference in vision between your two eyes. With the correct diopter adjustment, both eyes feel comfortable when observing.

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“What is the field of view in a microscope?”

The field of view is the diameter of the illuminated circle seen through the eyepiece. The higher the magnification, the smaller the field of view. To get the exact value of your microscope’s field of view, place a clear ruler under the microscope lens and count how many millimeter divisions fit within the visible circle of light.

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“What is the difference between achromatic, planachromatic, semi-apochromatic and apochromatic lenses?”

The main difference between the microscope objectives is in the design, image quality and examination methods.

Achromatic lenses feature reduced spherical and chromatic aberrations. This type of lens has a flat field of focus in the middle 65% of the field of view. The delivered image may have a blue-red tinge.

Plan achromatic lenses correctly for chromatic aberration. They flatten the field of view to provide a very sharp image across the entire frame. These lenses are excellent for macro photography.

Semi-apochromatic lenses have an average image quality (compared to achromatic and planachromatic lenses). The optical elements in these objectives contain fluorite, which allows them to be used in fluorescence microscopy.

Apochromatic lenses (compared to achromatic lenses) produce a sharper image with clearer colors. This is achieved through an enlarged spectral range.

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“Can I see germs with a microscope?”

You will not be able to observe germs with an amateur microscope. The reason it’s impossible is because they’re too small. You can only observe germs with a microscope that can provide at least 1200x magnification and the specimen must be stained. So you have to use a fairly powerful microscope model and special methods of sample preparation. Of course, bacteria also have giants that can be seen even at 900x magnification, but they live in the deepest depths of the ocean and it’s virtually impossible to get hold of these specimens.

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Lára has a degree in Life Sciences from Oxford University and has been working as a Science Tutor in the UK for several years now. Lára has a particular interest in infectious diseases and epidemiology and enjoys creating original educational materials that build confidence and facilitate learning.

Why is biological magnification important in biology?

Like it or not, there are toxins in many of the foods we eat. A well-known toxin is mercury, which is found in high concentrations in certain fish. When you eat a fish, you also consume the mercury it may contain, and in large concentrations, mercury can have serious effects on the human body. Other toxic substances include the chemical bisphenol-A (BPA), found in some plastic containers that can leach into food, and polycyclic aromatic hydrocarbons (PAH), a by-product of grilling meat.

To understand biological magnification, it is important to understand how the food chain works. In the food chain there are producers and consumers. Producers make their own food and don’t have to physically eat anything. Plants are the main producers because they use the sun’s energy to make their own food (through photosynthesis). Consumers who eat producers (plants) are called herbivores; Consumers who eat other consumers are called carnivores; and consumers who eat both are called omnivores. Through bioaccumulation, all organisms build up toxic substances over time. When one of these organisms is eaten, all of its toxins are eaten along with it, increasing this toxic accumulation at each step in the food chain.

Since the introduction of pesticides and herbicides, there has been an increasing number of toxic substances that can biomagnify. The once widespread insecticide DDT was banned for agricultural use in many countries in the 1970s, but can still be found in the bodies of some animals today. It was particularly harmful to bald eagles, which ate fish contaminated with the chemical that had entered water bodies. The DDT caused the eagle egg shells to become thinner, resulting in fewer hatchlings. Because of this, the bald eagle nearly went extinct, and it has taken decades for its population to recover since the DDT ban.