Echoes Within

👁️🔭 Summary Note: Light – Defects of Human Eye, Microscope & Telescope

In Light 3, here’s a clear and concise summary note for the lesson “Light 3 – Defects of Human Eye, Microscope & Telescope”, tailored for SEE-passed students preparing for NEB Grade 11 Science entrance exams.

👁️ A. Human Eye and Its Defects

🔹 Structure of the Human Eye:

• Cornea – transparent front layer that refracts light.

• Iris – the colored part that controls pupil size.

• Pupil – opening through which light enters.

• Lens – focuses light on the retina.

• Retina – light-sensitive layer; forms image.

• Optic Nerve – carries visual signals to the brain.

• Ciliary Muscles – adjust lens shape for focusing.

⚠️ Common Defects of Vision:

🔬 B. Microscope

🔹 Simple Microscope:

• Uses a single convex lens.

• Magnifies small objects (like a magnifying glass).

• Used for low magnification (2x–10x).

🔹 Compound Microscope:

• Uses two convex lenses: the objective and eyepiece.

• Objective forms a real, inverted image.

• The eyepiece magnifies it to form a virtual, enlarged image.

• Used in biology and laboratories for viewing tiny details.

🔭 C. Telescope

🔹 Astronomical Telescope:

• Used to view distant celestial objects.

• Uses two convex lenses:

  • Objective lens: collects light and forms a real image.

  • Eyepiece lens: magnifies the image.

• The image formed is inverted and magnified.

• Used in astronomy.

🔹 Terrestrial Telescope:

• Includes a third lens to make the final image erect for viewing objects on Earth.

📝 Key Differences (Microscope vs Telescope):