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Qns on Laser

  1. May 17, 2006 #1

    i have this Qns as follows :

    which of the following statements about laser is incorrect?

    a. Laser light can be focused to a tiny spot.
    b. Laser light must be visible.
    c. Laser light travels in vacuum at a speed of 3 X 10^8 m/s
    d. Laser light can be extremely powerful.
    e. Laser light is monochromatic.


    for (b.) must laser light neccessaryly must be visible? can't it be in a non- visible spectum.

    for (d.) the ans seems horrible unsciencetific, although i agree that laser can be powerful.

    for (e.), i checked up wikipedia can found this:
    "In the physical sense, no real source of electromagnetic radiation is purely monochromatic, since that would require a wave of infinite duration. Even sources such as lasers have some narrow range of wavelengths (known as the linewidth or bandwidth of the source) within which they operate."

    what does this whole chunk mean can anyone explain?? what is wave of infinite duration?? and what is monochromatic??
  2. jcsd
  3. May 18, 2006 #2
    so what is the correct ans actually?
    Last edited: May 18, 2006
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