The Thin Lens Equation The Thin Lens Equation
- Slides: 18
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). • 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
The Thin Lens Equation
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.
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.
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
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 = 12 cm
Copy Table 1, Pg 566 into your notes
Homework • Pg 566 # 1 4
The Magnification Equation
The Magnification Equation Where M = magnification of the image Magnification has no units as they will cancel out.
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.
Example 1: An Ipod has a height of 11 cm 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?
Example 2: • An Ipod has a height of 11 cm 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?
Example 3: A toy rocket is placed 12 cm away from a diverging lens. An upright, virtual image is noticed 9. 0 cm on the same side as the rocket. What is the magnification of the lens?
Homework • Pg 566 # 5 8
- Thin lens magnification equation
- Amy nau
- Diane markoff
- Thin converging lens
- A lens produces a sharply focused
- Gaussian lens formula
- Matrix lens
- Converging vs diverging lens
- Fresnel and fraunhofer difference
- Convex vs concave lens
- Maximum lift coefficient formula
- Converging lens equation
- Magnification equation lens
- Magnification of lens
- Refraction by a lens
- Power of lens
- Sign convention for lenses in tabular form
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