An astronomical telescope has objective eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective lens, the lenses must be separated by a distance,

• 46.0 cm

• 50.0 cm

• 54.0 cm

• 37.3 cm

C.

54.0 cm

According to a question,

Focal length of the objective lens, F_o = +40 cm
Focal length of eyepiece, F_e = 4 cm
Object distance for objective lens (u_o) = -200 cm
Applying lens formula for objective lens,





Image will be formed at the focus of a eyepiece lens.

So, for normal adjustment distance between objectives and eyepiece (length of tube) will be,