Which of the following is FALSE?

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  1. Simple microscope is also known as magnifying glass.
  2. Refractive index of a medium is constant.
  3. Magnification produced by a lens is related to the object-distance and the image-distance.
  4. A ray of light passing through the optical centre of a lens, after refraction from a convex lens, will emerge parallel to the principal axis.

Answer (Detailed Solution Below)

Option 4 : A ray of light passing through the optical centre of a lens, after refraction from a convex lens, will emerge parallel to the principal axis.
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Detailed Solution

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The correct answer is option 4.

Key Points

  • A ray of light passing through the optical center of a lens does not bend; it continues in the same direction.
  • In convex lenses, rays passing through the optical center are not refracted and thus do not emerge parallel to the principal axis.
  • Convex lenses converge light rays that are parallel to the principal axis to a focal point.
  • Option 4 incorrectly states that a ray of light passing through the optical center of a convex lens will emerge parallel to the principal axis, which is false.

Additional Information

  • Simple Microscope
    • A simple microscope, also known as a magnifying glass, consists of a single convex lens.
    • It is used to magnify small objects for better visibility.
  • Refractive Index
    • The refractive index of a medium is a measure of how much the speed of light is reduced inside the medium compared to a vacuum.
    • It is a constant property for a given medium under specific conditions.
  • Magnification by a Lens
    • Magnification produced by a lens is the ratio of the image height to the object height.
    • It depends on the object distance (u) and the image distance (v) from the lens.
  • Optical Center
    • The optical center of a lens is a point on the principal axis where a light ray passes through without being refracted.
    • In convex lenses, rays passing through this point continue in the same direction.
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