Chiếu một chùm tia X đơn sắc vào một lá kim loại thì thấy lá kim loại tích điện. Dùng một tĩnh điện kế một đầu nối với lá kim loại, đầu còn lại nối đất thì thấy tĩnh điện kế chỉ hiệu điện thế U = 1500 V. Công thoát của electron bật khỏi kim loại Α = 3,54 eV. Bước sóng λ của tia X bằng:                 

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Một số câu hỏi khác có thể bạn quan tâm.

• Choose the word that has the underlined part pronounced differently from the rest:  

  honey                  dove                      go                     young

• Choose a word that has different stress pattern:

  profession                personality                     activity                     selection

• Find a mistake in the four underlined parts of the sentence and correct it:

  There is no need to asking her about her school results.

• Find a mistake in the four underlined parts of the sentence and correct it:

  An has been sleeping for two hours what the telephone rang.

• Choose the best answer for the following sentence:

  He wants to know about my sister’s martial status so he asked her: "_____________ ?"
  
  

• Choose the best answer for the following sentence:

  ____________ is the distance from here to the airport?
  
  

• Choose the best answer for the following sentence:

  It’s my hobby to ______________ my favourite bike to school every morning.
  
  

• Choose the best answer for the following sentence:

  He didn’t get good mark ____________ he worked very hard.
  
  

• Choose the best answer for the following sentence:

  Ngoc: “______________ you to school on your first day?”

  Hoai: “My mother did.”
  
  

• Choose the best answer for the following sentence:

  Van: “Is this my new bike, father?”

  Father: “Yes, what _____________?”