Question

Compare astronomical telescope with compound microscope. Can a telescope be used as a microscope and vice-versa? Explain with reason.

Hint:

Telescope $\rightarrow$ distant objects; Microscope $\rightarrow$ tiny near objects.

Answer 1

Step 1: Astronomical telescope.
- Consists of two convex lenses: objective (long focal length) and eyepiece (short focal length).
- Objective forms a real, inverted, diminished image of distant objects; eyepiece magnifies it.
- Used for viewing far-away objects like stars and planets.
Step 2: Compound microscope.
- Also consists of two convex lenses: objective (short focal length) and eyepiece (moderate focal length).
- Objective forms a real, magnified image of a tiny nearby object, which is further magnified by the eyepiece.
- Used for studying minute objects.
Step 3: Comparison.
- Telescope: long $f_{obj}$, designed for distant sources.
- Microscope: short $f_{obj}$, designed for very near sources.

Step 4: Reason for non-interchangeability.
- A telescope cannot be used as a microscope because its long focal length objective cannot form magnified images of near objects.
- Similarly, a microscope cannot be used as a telescope because its short focal length objective is not suitable for forming images of distant objects.
Step 5: Conclusion.
Thus, both instruments serve different purposes and cannot replace each other.