19. The figure shows two spaceships moving directly away from us. Ship A (in front) emits a light signal at wavelength 500 nm (as measured by the ship occupants). Ship B (in pursuit) detects that signal at wavelength 600 nm. Ship B is moving at speed 0.200c relative to us. What is the wavelength (nm) of the signal as we detect it?

(A) 1235
(B) 735
(C) 1100
(D) 312
(E) 276
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統計: 尚無統計資料
統計: 尚無統計資料