题干

2011年2月14日,美国“星尘号”探测器逐渐飞近坦普尔1号彗星,探测器间歇性地向彗星发射____(电磁波/超声波/次声波)信号,当发出信号____ s后就能接收到经彗星反射回的信号时,即可断定两者间距为180km(v电磁波=3×108 m/s,v声=340m/s).此时探测器上的照相机自动拍摄得到如图所示的彗星图片,若像距为15cm,则镜头的焦距为略____(大于/小于)15cm.

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电磁波,1.2×10﹣3,小于

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Monthly Talks at London Canal Museum

    Our monthly talks start at 19:30 on the first Thursday of each month except August. Admission is at normal charges and you don't need to book. They end around 21:00.

November 7th

    The Canal Pioneers, by Chris Lewis. James Brindley is recognized as one of the leading early canal(运河) engineers. He was also a major player in training others in the art of canal planning and building. Chris Lewis will explain how Brindley made such a positive contribution to the education of that group of early“civil engineers”.

December 5th

    Ice for the Metropolis, by Malcolm Tucker. Well before the arrival of freezers, there was a demand for ice for food preservation and catering(保存和供应),Malcolm will explain the history of importing(进口) natural ice and the technology of building ice wells, and how London's ice trade grew.

February 6th

    An Update on the Cotswold Canals, by Liz Payne. The Stroudwater Canal is moving towards reopening. The Thames and Severn Canal will take a little longer. We will have a report on the present state of play.

March 6th

    Eyots and Aits-Thames Islands, by Miranda Vickers. The Thames has many islands. Miranda has undertaken a review of all of them. She will tell us about those of greatest interest.

Online bookings: www.canalmuseum.org.uk/book

More info: www.canalmuseum.org.uk/whatson

London Canal Museum

12-13 New Wharf Road, London NI 9RT

www.canalmuseum.org.uk   www.canalmuseum.mobi

Tel:020 7713 0836