The television camera is rather like the human eye．Both the eye and the camera have a lens(镜头)，and both produce a picture on a screen．In each case the picture is made up of millions of spots of light．

　　Let us see how the eye works．When we look at an object a person, a house, or whatever it may be we do not see all the details of the object in one piece．We imagine what we do, but this is not the case．In fact, the eye builds up the picture for us in our brain, which controls our sight, in millions of separate parts, and, although we do not realize it, all these details are seen separately．

　　This is what happens when we look at something．Beams of light of different degrees of intensity(强度), reflected from all parts of the object, strike the lens of the eye．The lens then gathers together the spots of light from these beams and focuses them on to a light sensitive plate the retina(视网膜)at the back of the eyeball．In this way an image of the object is produced on the retina in the form of a pattern of lights．

　　The retina contains millions of minute light sensitive elements, each of which is separately connected to the brain by a tiny fibre in the optic(视力的)nerve．These nerve fibres, working independently, pick out minute details from the image on the retina and turn the small spots of light into nerve impulses(冲击)of different strengths．They then transmit these impulses to the brain．They do this all at the same time．

　　All the details of the image are fed to the brain, and, as we have taught our brain to add them together correctly, we see a clear picture of the object as a whole．

　　Television, which means vision at a distance, operates on a similar principle．A television picture is built up in thousands of separate parts．

　　Beams of light reflected from the subject being televised strike the lens of the television camera, which corresponds to(相当于)the lens of the eye．The camera lens gathers together the spot of light from these beams and focuses an image of the subject on to a plate, the surface of which is coated with millions of photo electric elements sensitive to light．

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阅读理解

　　I don't ever want to talk about being a woman scientist again．There was a time in my life when people asked constantly for stories about what it's like to work in a field dominated by men．I was never very good at telling those stories because truthfully I never found them interesting．What I do find interesting is the origin of the universe, the shape of space-time and the nature of black holes．

　　At 19, when I began studying astrophysics(天体物理学), it did not bother me in the least to be the only woman in the classroom．But while earning my Ph．D．at MIT and then as 3 post-doctor doing space research, the issue started to bother me．My every achievement－jobs, research papers, awards－was viewed through the lens of gender(性别)politics．So were my failures．Sometimes, when I was pushed into an argument on left brain versus(相对于)right brain, or nature versus nurture(培育), I would instantly fight fiercely on my behalf and all womankind．

　　Then one day a few years ago, out of my mouth came a sentence that would eventually become my reply to any and all provocations：I don't talk about that anymore．It took me 10 years to get back the confidence I had at 19 and to realize that I didn't want to deal with gender issues．Why should curing sexism be yet another terrible burden on every female scientist? After all, I don't study sociology or political theory．

　　Today I research and teach at Barnard, a women's college in New York City．Recently, someone asked me how many of the 45 students in my class were women．You cannot imagine my satisfaction at being able to answer：45．I know some of my students worry how they will manage their scientific research and a desire for children．And I don't dismiss those concerns．Still, I don't tell them "war" stories．Instead, I have given them this：the visual of their physics professor heavily pregnant doing physics experiments．And in turn they have given me the image of 45 women driven by a love of science．And that's a sight worth talking about．

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　　“would almost rather see you dead,”Robert S．Cassatt, a leading banker(银行家)of Philadelphia, shouted when his twenty-year-old eldest daughter announced that she wanted to become an artist．In the 19th century, playing at drawing or painting on dishes was all right for a young lady, but serious work in art was not．And when the young lady’s family ranked among(跻身于)the best of Philadelphia’s social(社交界的)families, such an idea could not even be considered．

　　That was how Mary Cassatt, born 1844, began her struggle as an artist．She did not tremble before her father’s anger．Instead, she opposed(抗拒)him with courage and at last made him change his mind．Mary Cassatt gave up her social position(社会地位)and all thought of a husband and a family, which in those times was unthinkable for a young lady．In the end, after long years of hard work and perseverance(坚持)，she became America’s most important woman artist and the internationally recognized leading woman painter of the time．

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