1 / 18

The Thin Lens Equation

The Thin Lens Equation. The Thin Lens Equation. Let’s us predict mathematically the properties of an image produced by a lens. Defining Variables. f = focal length, distance from the focus to the optical centre (F and F’ are the same distance from O).

norah
Download Presentation

The Thin Lens Equation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Thin Lens Equation

  2. The Thin Lens Equation • Let’s us predict mathematically the properties of an image produced by a lens

  3. Defining Variables • f = focal length, distance from the focus to the optical centre (F and F’ are the same distance from O). • do = distance from the object to the optical centre • di= distance from the image to the optical centre • ho = height of the object • hi = height of the image

  4. The Thin Lens Equation

  5. Sign Conventions • Object distances (do) are always positive. • Image distances (di) are positive for real images and negative for virtual images. • The focal length (f) is positive for converging lenses and negative for diverging lenses.

  6. To rearrange the equation, you need 3 basic math skills: 1. Cross the ­­­­­line, change the sign. To move a term to the other side of an equal sign; switch the “+” or “-”. 2. How to cross multiply, if it is on the top; then on the other side it is on the bottom and vice versa. 3. How to inverse an equation; basically you put a one over it as the one becomes the top half of a fraction.

  7. Example 1: A converging lens has a focal length of 25 cm. A light bulb is 60 cm away from the lens. Where will the image be formed? • Ans: di = +43 cm

  8. Example 2: • A diverging lens has a focal length of 30 cm. A flower is placed 20 cm away from the lens. Where will the image be formed? • Ans: di = -12cm

  9. Copy Table 1, Pg 566 into your notes

  10. Homework • Pg 566 # 1-4

  11. The Magnification Equation

  12. The Magnification Equation Where M = magnification of the image Magnification has no units as they will cancel out.

  13. Sign Conventions • Object height (ho) and image height (hi) are positive when measured upward from the principal axis (PA) and negative when measured downward. • Magnification (M) is positive for an upright image and negative for an inverted image.

  14. Example 1: An Ipod has a height of 11cm is balanced in front of a converging lens. An upright, virtual image is noticed with a height of 17 cm occurs on the same side. What is the magnification of the lens?

  15. Example 2: • An Ipod has a height of 11cm is balanced in front of a converging lens. An inverted, real image is noticed with a height of 38.5 cm on the opposite. What is the magnification of the lens?

  16. Example 3: A toy rocket is placed 12 cm away from a diverging lens. An upright, virtual image image is noticed 9.0cm on the same side as the rocket. What is the magnification of the lens?

  17. Homework • Pg 566 # 5-8

More Related