Question

A telescope has an objective lens of focal length 150 cm and an eyepiece with focal length 1.5 cm. If this telescope is used to see a 50 m tall building at a distance of 1.5 km, what is the height of the image of the building formed by the objective lens?

• A. 10 cm
• B. 5cm
• C. 20 cm
• D. 15 cm

Answer 1

Answer: (B)

For objective (convex) lens $\frac{2{\eta }^2}{g{a}^2}$ Here, $\frac{{\eta }^2}{g{a}^2}$ $\frac{{\eta }^2}{2g{a}^2}$ $\frac{{\eta }^2}{4g{a}^2}$ $t_1$ $t_2$ $2g(t_1+t_2)$ $\frac{g}{4}{(t_1+t_2)}^2$ $g/4(t_1{t}_2)$ Magnification $2g{\left(\frac{t_1+t_2}{4}\right)}^2$ $R/4$ $R/2$ $R/8$ $\left\{\frac{{(1+e)}^2}{1+e^2}\right\}\sqrt{\frac{gh}{2}}$