MCQ Detailed View

A simple microscope is a basic optical device that uses a single convex lens to magnify small objects, making them appear larger to the human eye. The magnifying power of a microscope refers to how many times bigger the image appears compared to the actual object. This magnifying power mainly depends on the focal length of the lens used in the microscope.

The magnification of a simple microscope is given by the formula:

M=1+DfM = 1 + \frac{D}{f}M=1+fD

where:

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  M = magnifying power

  
  


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  D = least distance of distinct vision (approximately 25 cm for a normal human eye)

  
  


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  f = focal length of the lens

  
  

From the formula, it is clear that the magnifying power is inversely proportional to the focal length of the lens. This means that if the focal length is made shorter, the magnifying power increases significantly. A lens with a small focal length bends light rays more sharply, producing a larger image on the retina of the eye.

For example:

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  A lens with 10 cm focal length will produce a smaller magnification compared to a lens with 5 cm focal length, assuming both are used under the same conditions.

  
  

Other factors like the aperture of the lens (the opening that allows light to pass) can affect the brightness and clarity of the image but not the magnifying power itself. Therefore, using a lens of short focal length is the most effective way to increase magnification in a simple microscope.

This principle is widely applied in designing magnifying glasses, jewelers’ loupes, and handheld microscopes, where higher magnification is needed to observe fine details of small objects.

In conclusion, the magnifying power of a simple microscope can be increased by decreasing the focal length of its lens, making it a key concept in optical physics and basic microscopy.