A school telescope has an objective of focal length 150 cm and an eyepiece of focal length 3.0 cm…

Step 1. The magnifying power. $|m| = \dfrac{f_o}{f_e} = \dfrac{150\ \text{cm}}{3.0\ \text{cm}} = 50$.

Step 2. The length. $f_o + f_e = 150\ \text{cm} + 3.0\ \text{cm} = 153\ \text{cm}$.

Step 3. The angle of the image. $\beta = |m|\alpha = 50 \times 0.50^\circ = 25^\circ$.