问题 填空题

太阳、地球、月亮、平面镜,其中属于光源的是______.光在真空中的传播速度是______m/s,太阳到地球的距离为1.5×108km,那么太阳光射到地球表面上需______s.

答案

①太阳自身能够发光,属于光源;月亮、地球、平面镜只是反射了太阳光,本身不能发光,所以月亮不是光源.

②光在真空中的传播速度是3×108m/s,合3×105km/s,

太阳发出的光传播到地球需时间:

t=

s
v
=
1.5×108km
3×105km/s
=500s.

故答案为:①太阳;②3×108;500.

单项选择题

Public speaking fills most people with dread. Humiliation (羞辱) is the greatest fear; self-exposure and failing to appeal to the audience come a close second. Women hate it most, since girls are pressurized from an early age to be concerned with appearances of all kinds.
Most people have plenty of insecurities, and this seems like a situation that will bring them out. If you were under pressure to be perfect, you are terrified of falling in the most public of ways.
While extroverts (性格外形者) will feel less fear before the ordeal, it does not mean they will necessarily do it better. Some very shy people manage to shine. When I met the British comedian Julian Clary, he was shy and cautious, yet his TV performances are perfect.
In fact, personality is not the best predictor of who does it well. Regardless of what you are like in real life, the key seems to be to act yourself.
Actual acting, as in performing the scripted lines of a character other than yourself, does not do the job. While politicians may limit damage by having carefully rehearsed, written scripts to speak from, there is always a hidden awareness among the audience that the words might not be true.
Likewise, the incredibly perfect speeches of many American academics are far from natural. You may end up buying their book on the way out, but soon afterwards, it is much like fast food, and you get a nameless sense that you’ve been cheated.
Although, as Earl Spencer proved at his sister Princess Diana’s funeral, it is possible both to prepare every word and to act naturally. A script rarely works and it is used to help most speakers. But, being yourself doesn’t work either. If you spoke as if you were in your own kitchen, it would be too authentic, too unaware of the need to conmmnicate with an audience.
I remember going to see British psychiatrist R. D. Laing speak in public. He behaved like a seriously odd person, talking off the top of his head. Although he was talking about madness and he wrote on mental illness, he seemed to be exhibiting rather than explaining it.
The best psychological place from which to speak is an unselfconscious self-consciousness, providing the illusion of being natural. Studies suggest that this state of "flow", as psychologists call it, is very satisfying.

Women hate public speaking most mainly because of______.

A.their upbringing very early on

B.their inability to appeal to the audience

C.their sense of greater public pressure

D.their sense of greater humiliation

单项选择题