Một hồ nước yên tĩnh có bề rộng 9m. Trên bờ hồ có một cây cột cao 3m có treo một bóng đèn ở đỉnh. Một người đứng bên bờ hồ đối diện quan sát ảnh của bóng đèn, mắt người này cách mặt đất 1.5m a, Vẽ chùm tia sáng từ bóng đèn phản xạ trên mặt nước tới mắt người quan sát? b, Người ấy lùi xa bồ hồ tới khoảng cách bằng bao nhiêu thì sẽ không còn nhìn thấy ảnh của bóng đèn? Vẽ hình

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