2. Sample Papers
  3. NEET

NEET Sample Paper NEET Sample Test Paper-91

  • question_answer
    A telescope has an objective lens of focal length 150 cm and an eyepiece of focal length 5 cm. If a 50 m tall tower at a distance of 1 km is observed through this telescope in normal setting, the angle formed by the image of the tower is \[\theta ,\] then \[\theta \] is close to:

    A) \[30{}^\circ \]                          

    B) \[15{}^\circ \]

    C) \[84{}^\circ \]              

    D)        \[1{}^\circ \]

    Correct Answer: C

    Solution :

    [c] Magnifying power of telescope, \[MP=\frac{\beta \left( \text{angle subtended by image at eye piece} \right)}{\alpha \left( \text{angle subtended by object on objective} \right)}\]Also, \[MP=\frac{{{f}_{0}}}{{{f}_{e}}}=\frac{150}{5}=30\] \[\alpha =\frac{50}{1000}=\frac{1}{20}\text{rad}\] \[\therefore \] \[\beta =\theta =MP\times \alpha \] \[=30\times \frac{1}{20}=\frac{3}{2}=1.5\,\text{rad}\] or, \[\beta =1.5\times \frac{180{}^\circ }{\pi }=84{}^\circ \]


You need to login to perform this action.
You will be redirected in 3 sec spinner