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Thin Lens Equation. Rules. Object distances are always positive . Distances of virtual images are negative, real are positive. Converging lens has a positive focal length. Diverging lens has a negative focal length. Example 1.
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Rules • Object distances are always positive. • Distances of virtual images are negative, real are positive. • Converging lens has a positive focal length. • Diverging lens has a negative focal length.
Example 1 A converging lens has a focal length of 17 cm. A candle is located 48 cm from the lens. What type of image will be formed, and where will it be located? f = 17 cm do = 48 cm di = ?
Example 2 A diverging lens has a focal length of 29 cm. A virtual image of marble is located in front of the lens. Where is the marble located? f = -29 cm do = ? di = -13 cm
Magnification • The magnification equation can be stated as: or
Rules • Earlier rules still apply • ho and hi are positive when measured upward from PA and negative when measured downward from PA • M is positive for an upright image and negative for an inverted image
Example 3 A toy of height 8.4 cm is balanced in front of a converging lens. An inverted, real image of height 23 cm is noticed on the other side of the lens. What is the magnification of the lens? ho = 8.4 cm hi = -23 cm M = ?