Further Questions on Lenses and Telescopes

1.Lenses

The data below refer to converging lenses.Fill in the blanks in the table.

object distance/cm	focal length/cm	image distance/cm		
30.0	40.0			
25.0	20.0			
20.0		20.0		
50.0	20.0			
	30.0	40.0		

2

F

   a)Complete the ray diagram above to show how the image of height hi is formed.
     b)Mark in the image distance v and the object distance u .
     c)Write in terms of ho and hi  the magnification produced by the lens.
     d)Show by using similar triangles that the magnification of the lens is also given by v/u

 3 A simple astronomical telescope in normal adjustment has an eyepiece lens with a focal length of 2cm and produces a magnification of 10. What is the focal length of the objective lens?

4. A simple astronomical telescope in normal adjustment has a total length of 78cm and produces an angular magnification of 12. What is the focal length of the objective lens?

5.An astronomical telescope has an objective of focal length 80.0cm and an eyepiece of focal length 5.0cm. The telescope is in normal adjustment and a distant object subtends an angle of 5.0 x10-3 radians at the objective.
Find:
a)	the length of the instrument
b)	the angular magnification it produces
c)	the size of the intermediate image (that is, the size of the image produced by the objective lens).

hi

ho