1. Phy2005 Applied Physics II Spring 2017 Announcements:
Today: compound lenses, micro-, telescope
Exam 3 April 10 in-class

2. Last time Definitions: object distance p image distance qhi ho f D
screen x
D-x
Last time
Definitions:
object distance p
image distance q
magnification M = hi/ho
Lens equation:

3. Q2 A diverging lens has a focal length of -12 cm
Q2 A diverging lens has a focal length of -12 cm. An object of height ho = 4 cm is placed 4 cm from the lens. Which is closest to the size of the image?
(1) 4 cm (2) 3 cm (3) 1 cm (4) 2 cm (5) 0 cm

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5. #8 S11 Exam 3. An object is placed at a distance of 80 cm from a thin lens along the axis. If a real image forms at a distance of 40 cm from the lens, on the opposite side from the object, what is the focal length of the lens in cm?
(1) (2) (3) (4) (5) 21.4

6. Optical Instruments Perfect Eye Nearsighted
Eye Glasses
Perfect Eye
Nearsighted
Nearsighted can be corrected with a diverging lens.
 A far object can be focused on retina.

7. A Farsighted Power of lens: diopter = 1/f (in m)
(+) diopter  converging lens
(-) diopter  diverging lens
Larger diopter
 Stronger lens (shorter f)

8. Material n Cornea 1.38 Aqueous Humor 1.33-1.34 Lens 1.41-1.45
Vitreous Humor
1.34
Air
1.00
Water
1.33

9. (two converging lenses)
Compound Microscope
(two converging lenses)
objective
eyepiece po qo pe
Magnified inverted virtual image qe
Real image formed by the objective lens  an object for the eyepiece lens
fo fe
po pe
qo qe
Mo Me
Each set follows lens
Equations!!!
M = MoMe = (-qo/po)(-qe/pe)
= (qo/po)(qe/pe)

10. M = MoMe = (-qo/po)(-qe/pe) = (qo/po)(qe/pe)
Magnification becomes larger qo >> po:
1/po + 1/qo = 1/fo
1/po ≈ 1/fo
The object should be put near the focal point of
the objective lens.

11. Virtual image (qe<0)
Q. In a compound microscope, the obj. lens has a focal length of 8 mm,
And the eyepiece has a focal length 40 mm. The distance between the
lenses is 200 mm. If the object is placed 8.4 mm from the obj. lens,
What would be the magnification?
Inverted (M<0)
but
Virtual image (qe<0)
M = (qo/po)(qe/pe)
po = 8.4
qo = ?
fo = 8
D = 200
pe = ?
qe = ?
fe = 40
= (168/8.4)(-160/32) = -100
1/po + 1/qo = 1/fo
1/qo = 1/fo – 1/po = 1/8 – 1/8.4
qo = 168
pe = D – qo = 200 – 168
= 32
1/qe = 1/fe – 1/pe
= 1/40 – 1/32
qe = -160

12. Ex. 3 Two thin lenses with 10.0-cm focal lengths are mounted at
opposite ends of a 30.0-cm long tube. An object is located
45.0 cm from one end of the tube. How far from the opposite
end is the final image?
38.2 cm
12.8 cm
25.6 cm
(4) 33.6 cm
(5) 24.0 cm

13. #7 S11 Exam 3 Two thin lenses with focal lengths 50.0 cm and 60.0
cm are placed in contact in an orientation so that their optic axes
coincide. What is the focal length of the two in combination?
(1) 110 cm (2) 13.6 cm (3) 55.0 cm (4) 27.3 cm (5) 10.0 cm
(see section 27.13: Virtual objects)
(1) Object p1 and image q1 for lens 1 alone
(2) Object p2 and image q2 for lens 1 alone
Image of lens 1 is virtual object for lens 2
Add (1) and (2): effective focal length is

14. Telescope: angular magnification