If the tube length of an astronomical telescope is 105 cm and magnifying power is 20 for the normal setting, calculate the focal length of the objective.
Correct answer: A. 100 cm
- A. 100 cm
- B. 10 cm
- C. 20 cm
- D. 25 cm
Explanation
To calculate the focal length of the objective, we use the formula: Tube length, L = focal length of objective (fo) + focal length of eyepiece (fe). Given L = 105 cm and magnifying power = fo / fe = 20, we can solve for fe and then find fo. The correct answer is 100 cm. The other options are incorrect because they do not match the calculated focal length based on the given data.
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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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