Chap_26_Disc[1]

# Chap_26_Disc[1] - 26-32 During a daytime football game you...

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26-32: During a daytime football game you notice that a player’s reflective helmet forms an image of the Sun 4.8 cm behind the surface of the helmet. What is the radius of curvature of the helmet, assuming it to be roughly spherical? Picture the Problem : The image of the Sun forms behind the surface of a football player’s helmet. A ray diagram is shown at right. Strategy: Because the Sun can be considered infinitely far away, the rays from the Sun are approximately parallel. The resulting image of the Sun will occur exactly at the focal point of the helmet’s surface. Use equation 26-2 to calculate the radius of curvature. Solution: Calculate the radius of curvature:  i 22 2 4.8 cm 9.6 cm Rfd    Insight: For objects that are closer than the Sun, the image will be closer to the surface of the helmet. 26-45: A humorous scene in Akira Kurosawa’s classic film The Seven Samurai shows the young samurai Kikuchiyo wading into a small stream and plucking a fish from it for is dinner. (a) As Kikuchio looks through the water to the fish, does he see it in the general direction of point 1 or point 2 in the figure? (b) If the fish looks up at Kikuchiyo, does it see Kikuchiyo’s head in the general direction of point 3 or point 4? Picture the Problem : The young samurai Kikuchiyo wades into a small stream and plucks a fish from it for his dinner. Strategy: Note that a ray of light coming from the fish will bend away from the normal line when it emerges from the water. This refraction occurs at the surface of the water, but it is depicted above the surface of the water in the diagram at right for clarity. The ray path is reversible; it describes the path taken by rays from both the fish and the man’s head.

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Chap_26_Disc[1] - 26-32 During a daytime football game you...

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