The near point of a naked eye is 25 cm. When placed at the nearpoint and viewed

Question

The near point of a naked eye is 25 cm. When placed at the nearpoint and viewed by the naked eye, a tiny object would have anangular size of 5.2 X 10^-3 rad. (The minus sign indicates thatthe image produced by the microscope is inverted.) The objective ofthe microscope has a focal length of 2.9cm, and the distance between the objective and the eyepiece is 16cm. Find the focal length of the eyepiece. 1 cm X 10^-5rad. When viewed through a compound microscope, however, it has anangular size of -7.60

Explanation / Answer

Given that The near point of the object,N = 25 cm
Angular size of the object as viewed by naked eye, =5.2x10-5 rad
Angular size as observed through a compound microscope,' =-7.60x10-3 rad
focal length of the objective of the microscope,fo = 2.9cm
Distance between the objective and the eye piece,L = 16 cm Now the angular magnification is given by                      M = '/
                          = -7.60x10-3 /5.2x10-5                            =-146.15
For compound microscopes,
                      M = - (L-fe)N/fofe
               146.15 = (16 - fe) 25 / 2.9fe                 146.15= (400 -25fe)/2.9fe             423.846fe = 400 -25fe             448.835fe = 400                           fe = 400/448.835                             = 0.891cm             448.835fe = 400                           fe = 400/448.835                             = 0.891cm

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---