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一、像与斑的意义不明物体经透镜作里,折射光线会聚成实像.折射光线的反向延长线会聚成虚像.成像之前或成像之后被光异所截.肉眼所观察到的是光斑.光斑不是像,两者的物理含义是不同.倘若对像、斑(?)义不明了,也常引起解题失误.例1.把一点光源(?)在焦距为f的凸透镜的焦点上,在透镜的另一侧2倍焦距处放一个垂直主光怕的屏,在屏上可看到一个半径为R的光亮的圆.现保持透镜和光屏不动,面沿主光轴移动光源.若要使光屏上的亮圆半径缩小为R/2,则这个点光源应移
First, the meaning of the image and the point of the unknown object through the lens, the refracted light will converge into a real image. The refraction of the light will be converged into a virtual image. Before or after the image is cut by the light. The naked eye observes the light spot. The spot is not like, the physical meaning of the two is different. If the object, spot (?) meaning is unknown, it often causes problem solving. Example 1. Put a point light source (?) in the focal point of the convex lens of the focal point f, Place a vertical main light fear screen at the other side of the lens at 2x focal length. A bright circle with a radius of R can be seen on the screen. Now the lens and screen are kept fixed, and the surface moves the light source along the main optical axis. To reduce the bright circle radius on the screen to R/2, this point source should be shifted