Lecture%2038%202220%20Spring%202009

# Lecture%2038%202220%20Spring%202009 - Reminders and...

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1 Reminders and Announcements • Exam 3 is this afternoon at 4:15 (Chs. 31-34) HW 22 is due Friday • HW 22 is due Friday • Help Room Hours (Physics 117): – M 4-8 pm, T 3-6:30, W 3-6:30, R 4:30-8, F 2-6 Lens Makers’ Equation • The focal length of a thin lens is the image distance that corresponds to an infinite object distance – This is the same as for a mirror • The lens makers’ equation is 12 11 1 1 1 (1 ) ƒ n pq R R ⎛⎞ + =− − = ⎜⎟ ⎝⎠ Example Thin Lens Equation • The relationship among the focal length, the object distance and the image distance is the same as for a mirror 111 ƒ + = Notes on Focal Length and Focal Point of a Thin Lens • Because light can travel in either direction through a lens, each lens has two focal points – One focal point is for light passing in one direction through the lens and one is for light traveling in the opposite direction • However, there is only one focal length • Each focal point is located the same distance from the lens Focal Length of a Converging Lens • The parallel rays pass through the lens and converge at the focal point • The parallel rays can come from the left or right of the lens

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2 Focal Length of a Diverging Lens • The parallel rays diverge after passing through the diverging lens • The focal point is the point where the rays appear to have originated Determining Signs for Thin Lenses • The front side of the thin lens is the side of the incident light • The back side of the lens is where the light is refracted into • This is also valid for a refracting surface Sign Conventions for Thin Lenses Magnification of Images Through a Thin Lens
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Lecture%2038%202220%20Spring%202009 - Reminders and...

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