缝衣针都是亮亮的,你怎样将它变黑呢?当然不许用任何其他东西．把针扎成一捆,针尖朝上,我们从上面看下去,除了最外面一层外,其余部分的针尖都变成黑色了．我们知道,缝衣针是经过电镀的,单根针能反射90％的光线,所以看起来是闪亮的．但如果把针捆成一捆,光线倾斜地照射在针尖上,就会在每两根针尖之间发生连续 The sewing needles are bright, how do you make it black? Of course you can’t use anything else. The needles are bundled into a bundle with the tip pointing up. As we look from above, except for the outermost layer, the rest of the needles are black. We know that the sewing needle is electroplated, and a single needle can reflect 90% of light, so it looks shiny. However, if the needles are bundled into a bundle, the light will irradiate obliquely on the needle tip and it will be continuous between every two needle tips.