焦点:平行于主光轴的光线经凸透镜折射后会聚在主光轴上一点(经凹透镜折射后要发散,折射光线的反向延长线相交在主轴上一点)这一点叫透镜的______,焦点到光心的距离,叫______,用______表示.
0 98571 98579 98585 98589 98595 98597 98601 98607 98609 98615 98621 98625 98627 98631 98637 98639 98645 98649 98651 98655 98657 98661 98663 98665 98666 98667 98669 98670 98671 98673 98675 98679 98681 98685 98687 98691 98697 98699 98705 98709 98711 98715 98721 98727 98729 98735 98739 98741 98747 98751 98757 98765 235360