21 - Thin Lens Equation - Notes PDF

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21 - Thin Lens Equation

SNC2D – Physics – Light and Geometric Optics

Date: ______________________________________________

The Thin Lens Equation When dealing with position, use Cartesian coordinate system conventions d o is measured from the axis of symmetry to the object on the _______________________ d i is measured from the axis of symmetry to the image on the _______________________ Virtual images will have a __________________________________________ distance Focal length is ____________________________ for a converging lens, ______________________________ for a diverging lens

f = ____________________________________________________________ d i = ____________________________________________________________ d o = ____________________________________________________________

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21 - Thin Lens Equation

SNC2D – Physics – Light and Geometric Optics

Examples Where does the image form when an object is placed 20 cm away from a converging lens which has a focal length of 10 cm?

Where does the image form when an object is placed 15 cm away from a converging lens which has a focal length of 10 cm?

Where does the image form when an object is placed 15 cm away from a diverging lens which has a focal length of –10 cm?

What is the focal length of a lens if the object is 10.0 cm away and the image is found 20.0 cm away?

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21 - Thin Lens Equation

SNC2D – Physics – Light and Geometric Optics

Magnification Equation

M = ____________________________________________________________ d i = ____________________________________________________________ d o = ____________________________________________________________ h i = ____________________________________________________________ h o = ____________________________________________________________

Negative magnification means that the object is ___________________________________________ (following Cartesian coordinate conventions) | |  1 means a smaller image | |  1 means a larger image

Examples What is the magnification of a diverging lens if the object height is 10 cm and the image height is 5 cm?

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21 - Thin Lens Equation

SNC2D – Physics – Light and Geometric Optics

What is the height of an object if it is 10 cm from a converging lens and the –10 cm image forms 20 cm from the lens?

What is the magnification of a converging lens (with a focal length of 6 cm) if the object distance is 10 cm from the lens?

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21 - Thin Lens Equation

SNC2D – Physics – Light and Geometric Optics

Homework Answer the following question with full and complete solutions. Watch your significant figures. 1. A 14 cm tall object is placed 26 cm away from a converging lens that has a focal length of 13 cm. How far from the lens will the image be formed? How tall is the image formed? 2. Suppose a 2.0 cm high object is 6.0 cm in front of a converging lens that has a focal length of 4.0 cm. Use the thin lens equation to find the location and height of the image. 3. A light bulb is placed a distance of 45.7 cm from a double convex (converging) lens having a focal length of 15.2 cm. Determine the image distance. What is the magnification of this lens? 4. Determine the focal length of a double concave (diverging) lens that produces an image that is –16.0 cm behind the lens when the object is 28.5 cm from the lens. 5. Suppose a 12 cm tall object is placed 30 cm from a converging lens which has a focal length of 12 cm. How far from the lens will the image be formed? What is the magnification of the lens? 6. A light bulb is placed a distance of 36.5 cm from a double concave (diverging) lens having a focal length of –12.7 cm. Determine the image distance. 7. Determine the focal length of a double convex (converging) lens that produces an image that is 16.0 cm from the lens when the object is 28.5 cm from the lens. 8. A 5.00 cm high object is placed to the left of a diverging lens which has a focal length of –5.00 cm. The magnification is 0.500. Find the distance to the object and the distance to the image. Do this with the thin lens equation and then, using your object distance, make a ray diagram to check your image distance.

Answers 1.  = 26

ℎ = −14 

2.  = 12

ℎ = −4 

3.  = 22.8

 = −0.5

4.  = −36.5 5.  = 20



 = −

6.  = −9.4 7.  = 10.2 8.  = 5.0

 = −2.5 Page 5 of 5...