AN ASYRONOMICAL TELESCOPE CONSISTS OF TWO THIN LENSES 36 CM APART AND HAS NORMAL MAGNIFYING POWER 8.CALCULATE FOCAL LENGTH OF LENSES.

Distance between the objective lens and the eyepiece of astronomical telescope = fo +  fe;

 

where fo = focal length of objective lens and fe = focal length of eye lens

Magnifying power, m = fo/fe;

 

36 = fo +  fe;

 

m = 8 = fo/fe;

 

36 = 8 fe + fe = 9 fe;

 

fe = 4 cm

 

and fo = 32 cm