Adv Physics

1
Adv Physics

• Chapter 23 Section 3
• Chapter 25 Section 1

2
Lenses

• Lens equation
• 1/f 1/d0 1/di
• Magnification equation
• m -di / do

3
Convex Concave
f -
do
di real - virtual - virtual
m upright - inverted upright
4
Sample Problem

• A 2 cm tall object is placed 7.5 cm to the left
  of a convex lens whose focal length is 11.8 cm.
  Find the image distance and determine whether the
  image is real or virtual. Determine the
  magnification and the image height.

5
Sample Problem

• An object is placed 7.1 cm to the left of a
  diverging lens whose focal length is 5.08 cm.
  Find the image distance and determine whether the
  image is real or virtual. Obtain the
  magnification.

6
The Eye

• Air to cornea (n1.38)
• Cornea to aqueous humor (n1.34)
• Aqueous humor to lens (n1.42)
• Lens to vitreous humor (n1.34)
• Light strikes the retina where image is formed

7
Accomodation

• Process of adjusting the shape of the lens to
  focus on different objects
• - accomplished using the ciliary muscles
• - muscles are relaxed to make the lens flatter
  to see distant objects
• - muscles are tightened to make the lens more
  curved to see close objects

8
Normal Vision

• Near point closest point that can be seen as a
  clear image
• - usually at about 25 cm from the eye
• Far point farthest object that can be seen as a
  clear image
• -so far away we call it infinity

9
Myopia

• Nearsighted
• Defect in the eye in which the eye is unable to
  see clearly distant objects
• Image formed by eye is in front of retina

10
Myopia

• Corrected using a concave lens
• Image is now formed at the far point
• Using a concave lens alters the near point!

11
Sample Problem

• Find the optical power necessary to correct an
  eye with a far point of 50 cm. Neglect the
  distance from the lens to the cornea.
• Hint Optical power 1/f
• If the eyes near point was 10 cm, what is the
  eyes corrected near point?

12
Hyperopia

• Farsighted
• Defect of the eye in which the eye is unable to
  see close objects
• Image is formed behind the retina

13
Hyperopia

• Corrected using a convex lens
• Image is now formed at the near point
• Using a convex lens alters the far point!

14
Sample Problem

• Find the power of a lens designed for reading
  purposes to correct an eye with a near point of
  75 cm. Assume a standard reading distance of 25
  cm. Neglect the distance from the cornea to the
  corrective lens.

15
Blind Spot

• Region of retina where there are no
  photosensitive receptors and the optic nerve
  leaves
• Approx 1.5 mm in diameter
• when image is formed on this spot it is lost

16
Fovea

• Most sensitive part of retina
• Near its center
• Approx 0.4 mm in diameter
• Image formed here is most clearly seen