An astronomical telescope has an objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance of :
(1) 46.0 cm

(2) 50.0 cm  

(3) 54.0 cm

(4) 37.3 cm 

In an astronomical telescope in normal adjustment a straight black line of length L is drawn on inside part of the objective lens. The eye-piece forms a real image of this line. The length of this image is l. The magnification of the telescope is:

(1)L/l+1

(2)L/l-1

(3)L+1/L-1

(4)L/l

If the focal length of the objective lens is increased, then magnifying power of :

(1) microscope will increase but that of telescope decrease

(2) microscope and telescope both will increase

(3) microscope and telescope both will decrease

(4) microscope will decrease but that of telescope will increase

The magnifying power of a telescope is 9. When it is adjusted for parallel rays the distance between the objective and eyepiece is 20cm. The focal length of lenses are 

(1) 10cm,10cm

(2) 15cm,5cm

(3) 18cm,2cm

(4) 11cm,9cm