Как изменялась площадь освещенной части при последовательном увеличении угла падения лучей на поверхность картонного квадрата без выреза?

Here come the New year! I'm with friends very much looking forward to this holiday and we to him diligently prepared. Dad brought a big tree and we with the guys her dressing. On top put an angel, branches decorated with garlands and balloons, hanged a lot of tinsel. Under the Christmas tree we put the Grandfather of the Frost and the snow maiden, but the room was decorated with all kinds of snowflakes, garlands and streamers. It turned out very nicely. Adults praised us for our diligence, and promised that Santa Claus is necessary for us to bring gifts. We are eagerly waiting for this moment, and every five minutes to look under the tree. But the gift is not there... We were very sorry and mom, that would distract us, called to drink tea with the cake. Then we played different games and participated in the competitions. It was very fun and we have forgotten that there would come a Grandfather frost. And when it came time to disperse, some of the guys looked under the tree and found a mountain of gifts . Everyone got what wanted. All were very happy. So that's my New Year's!