题干

用如图的装置研究电光效应现象,用能量为2.5eV的光子照射到光电管上时,电流表G示数不为0,移动变阻器的触点c,当电压表的示数大于或等于时0.7V,电流表示数为0,则下列说法中正确的是(   )

A:光电管阴极的逸出功为1.8eV

B:电键K断开后,没有电流流过电流表G

C:光电子的最大初动能为3.2eV

D:改用能量为1.5eV的光子照射,电流表G也有电流,但电流较小

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A

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    Businesses are witnessing a difficult time, which has in turn produced influence on consumers, desire to go green. However, shoppers are still laying stress on environmental concerns.

    Two thirds of customers say that environmental considerations inform their purchases to the same degree as they did a year ago, while more than a quarter say that they are now even better aware of the environmental effect on what they buy.

    This may help to influence how shops store goods on their shelves. And the companies should still make efforts to become more environmentally friendly. Two out of three people think it is important to buy from environmentally responsible companies, with about one in seven saying that they had even decided to take their custom elsewhere if they felt a company's environmental reputation was not good enough.

    Harry Morrison, chief executive (主管) of the Carbon Trust, sympathizes: “I understand this situation where survival is very important now. But from environmental considerations, the clock is ticking—we don't have much time. In addition, cutting carbon has an immediate effect as costs drop and a medium-term benefit for the brand.”

    Larger companies have an extra motivation to look at reducing their carbon footprint, as new rules next year will require businesses to buy carbon allowances to make up for their emissions (排放). Those that have taken early action will have a head start. More than two thirds of consumers are not clear about which companies are environmentally responsible. This suggests that firms that are able to relay clearly their message to the public will be in a pole position to attract shoppers.

    The Carbon Trust believes that it can help by informing customers about the good work companies are doing. “When companies are granted (授予) the standard, they can use a logo (标识) in all their marketing which makes it clear that they are working towards cutting emissions,” Mr. Morrison said.