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<p style="font-size:17px;line-height:30px;margin:10px 0px;color:#333333;font-weight:900;" data-flag="subtitle" lang="en">【第4.01讲】光的方向之谜：从欧几里得到阿尔哈森</p><p style="color:#333333;font-weight:normal;font-size:16px;line-height:30px;font-family:Helvetica,Arial,sans-serif;hyphens:auto;text-align:justify;" data-flag="normal" lang="en"><img data-key="0" src="http://imagev2.xmcdn.com/storages/894b-audiofreehighqps/49/DF/GKwRIRwIVg6WAAKbigImh8AD.jpg!op_type=4&upload_type=attachment&device_type=ios&name=mobile_large" alt="" data-origin="http://fdfs.xmcdn.com/storages/894b-audiofreehighqps/49/DF/GKwRIRwIVg6WAAKbigImh8AD.jpg" data-preview-width="140" data-large="http://imagev2.xmcdn.com/storages/894b-audiofreehighqps/49/DF/GKwRIRwIVg6WAAKbigImh8AD.jpg!op_type=4&upload_type=attachment&device_type=ios&name=mobile_large" data-large-height="191" data-preview="http://imagev2.xmcdn.com/storages/894b-audiofreehighqps/49/DF/GKwRIRwIVg6WAAKbigImh8AD.jpg!op_type=4&upload_type=attachm...