题干

如图所示是太阳能路灯,灯杆顶端是太阳能电池板,它能将太阳能转化为电能,并向灯杆下方的蓄电池充电,供夜晚路灯照明.若在一定时间内,太阳光辐射到该太阳能电池板的能量为2.4×107J,这些能量经转化后,可供功率为40W的路灯工作60h,则该太阳能路灯的能量转化效率为____ %.

 

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    We live in the world full of colours. Does a colour have weight? If you say “no”, you are wrong. If you don't believe, you may do an experiment.

    First, put two objects with the same weight into two boxes. Then cover the boxes. Third, wrap one box with a red piece of paper, the other woth a white piece of paper. Now hold the boxes with your hand one by one. It is certain that you think the red one is a little heavier.

    Why? A scientist found that different colours have different weight in a man's mind. So he did many tests and at last he found that every colour has its own weight in our mind and their order is the same. The heaviest colour is red, then blue, green, orange, yellow and white.

    The scientist told us that colours also have smell. Can you smell the colour? Of course not. Then why did the scientist say so? That is because every colour stands for a kind of light with a certain wavelength, and it reaches our brain through sense organs.

    According to this discovery, scientists say that people accept the colours they like, and refuse the colours they hate. So your body and mind will be healthy by using the colours you like. Or you'll be nervous or even get ill. For example, if you stay in a room with red windows, wallpapers and furniture for two hours, you'll feel you have been there for four hours. But if the room is blue, you'll feel you have been there for only an hour. Another example, if a person walks out of a red room and into a blue room, his temperature will fall. That means our body temperature will change with different colours.