Features:1. Unique paper material to check polarized sunglasses.2. Quick and easy to use, just put the card behind your sunglasses.3. See the difference through the polarized lens proves that the sunglasses are polarized.4. Bring great convenience to you，Good for your eyes and healthy.5. If your glasses are polarized, you can see the pattern, otherwise you will not see it.

Polarized test cardonline

The field of view in a microscope is calculated by dividing the field number by the magnification number.The field of view (FOV) is the observable area that can be seen through a microscope. It's a crucial aspect of microscopy as it determines the amount of a specimen that can be observed at once. The FOV is typically measured in millimetres (mm) or micrometres (µm), and it decreases as the magnification increases.To calculate the field of view, you need two pieces of information: the field number (FN) and the magnification number (MN). The field number is usually printed on the microscope eyepiece and represents the diameter of the field in millimetres. The magnification number is the magnifying power of the objective lens being used.The formula to calculate the field of view is: FOV = FN / MN. For example, if the field number is 20mm and the magnification number is 10x, the field of view would be 2mm.It's important to note that the field of view is inversely proportional to the magnification. This means that as the magnification increases, the field of view decreases. This is because the higher the magnification, the smaller the area of the specimen that can be observed at once. Therefore, when using a microscope, it's essential to find a balance between the level of detail required (which would require a higher magnification) and the amount of the specimen that needs to be observed (which would require a larger field of view).

Note:1.Due to the different monitor and light effect, the actual color of the item might be slightly different from the color which is showed on the pictures.2.Please forgive 1 cm/0.39"-3 cm/1.18" measuring deviation due to manual measurement.