Thực hiên giao thoa ánh sáng với nguồn gồm hai thành phần đơn sắc nhìn thấy có bước sóng λ₁ = 0,64μm; λ₂. Trên màn hứng các vân giao thoa, giữa hai vân gần nhất cùng màu với vân sáng trung tâm đếm được 11 vân sáng. Trong đó, số vân của bức xạ λ₁ và của bức xạ λ₂ lệch nhau 3 vân, bước sóng của λ₂ là:  

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Một số câu hỏi khác có thể bạn quan tâm.

• Choose one sentence that has the same meaning as the root one:

  He was possibly away as no one answered the phone.

   

   

• Choose the correct sentence which is built from the words and phrases given:

  I / have / a dream / a tornado / come / our house

   

   

• Choose a word that has different stress pattern:

  finger              elbow                culture                remove

• Choose a word that has different stress pattern:

  movement                 finish                  except              party

• Choose a word that has different stress pattern:

  attendance                 behavior                  position                  protocol

• Choose a word that has different stress pattern:

  especial               celebration                 interaction              reinforcement

• Choose a word that has different stress pattern:

  primarily                  congenial                acceptable                relationship

• Read the passage below and choose one correct answer for each question:

          Today the most important population trends are the fast growth in the number of elderly people and the sharp drop in the number of teenagers leaving school. The size of the elderly population is growing because people are living longer and fewer babies have been born.
          In 1911, only 5 percent of the UK population was older than 65. Today, the figure is more than 15 percent. Over the next decade the greatest increase will be in people aged 75 and over. The drop in the number of school-leavers was caused by the fall in the birth rate between 1964 and 1977. This trend is known as the "demographic time bomb" - because demographers knew that, once the birth rate fell, there was no way to stop it having an explosive effect on the economy and on society 16 years later.
          However, the impact may well be short-term. According to some forecasters the UK's birth rate may soon become one of the highest in western Europe. 

   

  1. What are the most important population trends today? - They are ___________.
  A. the fast growth in the number of elderly people
  B. the sharp drop in the number of teenagers leaving school
  C. the fewer babies
  D. A & B

  2. How many percent of the UK population was older than 65 in 1911?
  A. Only 5 percent.
  B. Only 15 percent.
  C. Only 25 percent.
  D. Only 10 percent.

  3. What will the greatest increase be in over the next decade?
  A. In people aged 75 and over.
  B. In people aged 65.
  C. In the number of school-leavers.
  D. In the newly born babies.

  4. What was the drop in the number of school-leavers caused by?
  A. The explosion in the birth rate between 1964 and 1977.
  B. The increase in the birth rate between 1964 and 1977.
  C. The fall in the birth rate between 1964 and 1977.
  D. the number in the birth rate between 1964 and 1977.

  5. According to some forecasters, what is the UK's birth rate like?
  A. It may soon become one of the highest in Europe.
  B. It may soon become one of the highest in the world.
  C. It may soon become one of the highest in western Europe.
  D. It may soon become one of the highest in eastern Europe.

   

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

  Do most woman in the world want to have a lot of children?

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

  What problems do population explosion cause to the world?