A microscope has an objective lens of focal length 1.40 mm and an eyepiece of focal length 20.00 mm.It is adjusted for minimum eyestrain for persons with a near point of 25.0 cm.A blood sample is placed 1.50 mm from the objective.The magnitude of the overall magnification is closest to
A)18.
B)37.
C)180.
D)370.

Question

Quizplus · Accepted Answer

The overall magnification is given by the product of the magnification of the objective lens and the magnification of the eyepiece. The magnification of the objective lens is given by:$$M_o = -d_o/f_o$$where $d_o$ is the object distance and $f_o$ is the focal length of the objective lens. The magnification of the eyepiece is given by:$$M_e = -d_e/f_e$$where $d_e$ is the image distance and $f_e$ is the focal length of the eyepiece.The overall magnification is then given by:$$M = M_o * M_e = (d_o/f_o) * (d_e/f_e)$$For minimum eyestrain, the image distance is equal to the near point of the observer, which is 25.0 cm. Therefore, we have:$$d_e = 25.0 cm = 0.250 m$$The object distance is given as 1.50 mm, which is 0.00150 m. Substituting these values into the equation for the overall magnification, we get:$$M = (0.00150 m/0.00140 m) * (0.250 m/0.0200 m) = 180$$Therefore, the magnitude of the overall magnification is closest to 180.

A Microscope Has an Objective Lens of Focal Length 1