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JEE Main & Advanced JEE Main Paper (Held On 10 April 2015)

  • 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 : JEE Main Online Paper (Held On 10 April 2015)

    A) \[{{60}^{o}}\]                                    

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

    C)  \[{{1}^{o}}\]                                     

    D) \[{{30}^{o}}\]

    Correct Answer: A

    Solution :

                     angular magnfication on \[m=\frac{{{f}_{0}}}{5}\frac{150}{5}=30\] so, \[\frac{\tan \beta }{\tan \alpha }=30\] \[\tan \beta =\tan \alpha \times 30=\left( \frac{50}{1000} \right)\times 30\] \[=\frac{15}{10}=\frac{3}{2}\]                     \[\beta K\approx {{60}^{o}}\]


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