An astronomical refractive telescope has an objective of focal length 20m and an eyepiece of focal length 2cm. (a) The length of the telescope tube is 20.02m. (b) The magnification is 1000. (c) The image formed is inverted. (d) An objective of a larger aperture will increase the brightness and reduce chromatic aberration of the image.
Here, f0=20mandfe=2cm=0.02m In normal adjustment, Length of telescope tube, L=f0+fe=20+0.02=20.02m and magnification, m=fef0=0.0220=1000 The image formed is inverted with respect to the object.
