It seems to be strange to you there is a blind spot (盲点)on the eyes. Here is an interesting experiment (实验) that can make something disappear(消失) when one eye is open.
Make a card which is as big as a postcard, and write two English letters L and R on it. Write L on the left and R on the right. First, hold the card about 80 cm(厘米) away and you see both the letters. Then close your right eye and look at the letter R only with your left eye. And now, as you move the card slowly towards you, you’ll find the letter L disappearing. But if you move the card nearer to your face, the letter will be seen again. Now do the same experiment with your left eye closed, you’ll find the letter R disappearing.
Why does the letter disappear? It is because there is a blind spot on the eye. When the image (影像) of the letter falls on the blind spot, it won’t be seen. That is why either of the letters disappears.
小题1: Where should we write the two letters?
小题2:Which letter should be written on the left?
小题3:Which eye do you close when R disappear?
小题4:What will happen if the image (影像) of the letter falls on the blind spot?
小题5:.Do all people know that there is a blind spot (盲点)on their eyes?