To examine a particular blood sample in biology lab, a student uses a compound m
ID: 1269503 • Letter: T
Question
To examine a particular blood sample in biology lab, a student uses a compound microscope set to have a magnification of -4525. The objective and eyepiece are both attached to a tube which is 17 cm in length and the eyepiece has a focal length of 2.53 cm. The near point of the person using the microscope is 25.5 and you can assume she can view the image produced with a fully relaxed eye.
1) What is the focal length of the objective?
f =_______cm
2.What is the distance between the blood sample and the objective lens?
do = _______cm
Explanation / Answer
For eye piece, assume v = 25.5 and f = -2.53 and calculate u1 for eye piece as
u1 = (25.5*2.53)/[25.5+2.53] =2.301 cm
This gives image distance from the objective as 16.5 - 2.301 = 14.199 cm
(14.199/d)*(25.5/2.301) = 4505 giving d = 0.035 cm
Applying lens formula, we get focal length of objective as (14.199*0.035)/[14.199+0.035] = 0.0349 cm