For normal adjustment, length of astronomical telescope is______________?
Correct answer: A. fo + fe
- A. fo + fe
- B. fo - fe
- C. fo / fe
- D. fe / fo
Explanation
In normal adjustment, the intermediate image formed by the objective lies at the focal point of the eyepiece, so the final image is at infinity. The distance between the lenses is therefore the sum of their focal lengths, L = fo + fe, where L, fo and fe are lengths. The likely mistake is choosing b, fo - fe, which applies a difference instead of the required separation sum.
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Light is studied through reflection, refraction, dispersion, interference, diffraction and polarization, linking ray behavior with its wave nature. Questions may involve mirrors, lenses, optical instruments, refractive index and image formation, while geometrical optics deals with rays and wave optics explains effects such as interference and diffraction.
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