Q. Two convex lenses of focal lengths $0.3 \, m$ and $0.05 \, m$ are used to make a telescope. The distance kept between the two in order to obtain an image at infinity is
NTA AbhyasNTA Abhyas 2022
Solution:
When the final image is formed at infinity by a telescope, it is called in normal adjustment and then the length of the telescope is given by
$L=f_{0}+f_{e}$
Where $f_{0}$ is the focal length of the objective lens and $f_{e}$ is the focal length of eye-piece
$\therefore L= \, f_{0}+f_{e}=0.3+0.05=0.35 \, m$
$L=f_{0}+f_{e}$
Where $f_{0}$ is the focal length of the objective lens and $f_{e}$ is the focal length of eye-piece
$\therefore L= \, f_{0}+f_{e}=0.3+0.05=0.35 \, m$