An insect 1.1 mm tall is placed 1.0 mm beyond the focal point of the objective l

Question

An insect 1.1 mm tall is placed 1.0 mm beyond the focal point of the objective lens of a compound microscope. The objective lens has a focal length of 14 mm , the eyepiece a focal length of 21 mm .

A) Where is the image formed by the objective lens? Give your answer as the distance from the image to the lens. Express your answer using two significant figures.

B) How tall is the image mentioned in part A? Express your answer using two significant figures.

C) If you want to place the eyepiece so that the image it produces is at infinity, how far should this lens be from the image produced by the objective lens? Express your answer using two significant figures.

D) Under the conditions of part C, find the overall magnification of the microscope. Express your answer using two significant figures.

Explanation / Answer

A) using 1/f = 1/u + 1/v we get
   1/14 = 1/15 + 1/v
   v = 210 mm is distance of image formed by objective lens from itself

B) Magnification = v/u = 210/15 = 14
   height of image =  1.1*14 = 15 mm

C) For final image at infinity, distance between eyepiece and image produced by objective, is equal to focal length of eyepiece. Hence distance is 21 mm

D) Overall magnification = Magnification of objective x ( D/ Ue)
D is minimum distance for clear vision = 250 mm
Ue is distance between image of objective and eyepiece
hence M = 14 * ( 250/ 21) = 170  

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.