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9. Ray optics abd optical instruments — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics9. Ray optics abd optical instruments1 Mark
MCQ
To increase both the resolving power and magnifying power of a telescope
  • ✓
    Both the focal length and aperture of the objective has to be increased
  • B
    The focal length of the objective has to be increased
  • C
    The aperture of the objective has to be increased
  • D
    The wavelength of light has to be decreased
✓

Answer

Correct option: A.
Both the focal length and aperture of the objective has to be increased
a
(a) Resolving power, $R=\frac{a}{1.22 \lambda}$

where, $a$ is diameter of objective $\lambda$ is wavelength of light

magnifying power $m=\frac{-f_{0}}{f_{e}}\left(1+\frac{f_{e}}{D}\right)$

so, decreasing the wavelength of light increases the resolving power and magnifying power of telescope.

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