Q29. A Galilean and a Keplerian telescope have equal positive objective focal lengths and eyepiece focal-length magnitudes. Both are adjusted for final image at infinity. Which statements are correct? (Select all correct options.)
Select all that apply

Question

Q29. A Galilean and a Keplerian telescope have equal positive objective focal lengths and eyepiece focal-length magnitudes. Both are adjusted for final image at infinity. Which statements are correct? (Select all correct options.)

Select all that apply

G1 Physics · Accepted Answer

This is MULTIPLE CORRECT. Both telescopes have objective focal length fₒ > 0; eyepiece focal-length magnitude = a > 0. A: TRUE. Galilean telescope has diverging eyepiece; its final image in normal adjustment is erect. B: FALSE. Keplerian uses a converging eyepiece, Lₖ = fₒ + a; Galilean uses a diverging eyepiece, Lɢ = fₒ − a. C: TRUE. Lₖ − Lɢ = (fₒ + a) − (fₒ − a) = 2a > 0, so Galilean is shorter. D: TRUE. Galilean telescope uses a concave (diverging) eyepiece. FINAL ANSWER: A, C and D.