Which one among the following is used in a simple microscope?

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UPSC CDS-I 2025 (General Studies) Official Paper (Held On: 13 Apr, 2025)
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  1. Diverging lens
  2. Concave mirror
  3. Converging lens
  4. Plane mirror

Answer (Detailed Solution Below)

Option 3 : Converging lens
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The correct answer is Converging lens.

Key Points

  • A simple microscope uses a converging lens (also known as a convex lens) to magnify objects.
  • The convex lens creates a magnified, virtual, and erect image of the object when placed at a distance shorter than the focal length of the lens.
  • It is commonly used for low-magnification observations, such as reading fine print or examining small objects.
  • The lens works based on the principle of refraction, bending light rays to converge and form an enlarged image visible to the human eye.
  • Simple microscopes are easy to use and are often utilized in educational and general-purpose applications.

Additional Information

  • Converging Lens (Convex Lens):
    • A lens that is thicker at the center than at the edges, capable of focusing light rays to a single point (focal point).
    • It is widely used in devices such as magnifying glasses, cameras, and telescopes.
    • The focal length determines the degree of magnification achievable by the lens.
  • Magnification:
    • Magnification refers to how much larger or smaller the image of an object appears compared to the object itself.
    • In a simple microscope, magnification is achieved by positioning the object within the focal length of the lens.
  • Virtual Image:
    • A virtual image is formed when light rays appear to diverge from a point, but do not actually meet.
    • In a simple microscope, the image is virtual, meaning it cannot be projected onto a screen.
  • Other Types of Lenses:
    • Diverging lens (concave lens): Produces a virtual, diminished image and is not used in simple microscopes.
    • Plane mirrors: Used to reflect light, but do not magnify images, hence unsuitable for microscopes.
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