Question
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Reflection and refraction problems: Do problems on pages 101-104 from your workshop activities manual. A stamp collector uses a magnifying lens that sits 2.0 cm above the stamp. The magnification is 4. What is the focal length of the lens? (2.7 cm). The filament of an incandescent light bulb (2 cm vertical height) serves as the real object for a thin converging lens. The filament is located 5.0 cm from the 0 cm end of an optical bench. The converging lens is placed at the 15 cm position on the optical bench. A sharp image of the filament is formed at the 80 cm mark on the optical bench. A schematic of the experimental arrangement is shown below. What is the object distance s? (20.0 cm) What is the image distance s'? (65.0 cm) Calculate the focal length f of the lens. (15.3 cm) Is the image real or virtual? Explain your answer, (real: Think about it!!) Is the image upright or inverted? Explain your answer, (inverted: Think about it!!) Calculate the image height.(6.50 cm)
Explanation / Answer
1) m = S'/S =====> S' = 2*4 = 8 cm
1/S + 1/S' = 1/F========> 1/2 + 1/8 = 1/F====> F = 8/5 = 1.6 cm
2)
a) S = 20 cm
b) S' = 80-15 = 65 cm
c) 1/F = 1/S + 1/S' = 1/20 + 1/65 ===>F = 15.29 cm
d) real
e) inverted
f) I/O = S'/S=========> I = 2*65/20 = 6.5 cm