A red laser from a physics lab is marked as producing 632.8 nm light. When light from this laser falls on two closely spaced slits, and inte

Question

A red laser from a physics lab is marked as producing 632.8 nm light. When light from this laser falls on two closely spaced slits, and interference pattern formed on a wall several meters away has bright fringes spaced 5.00 mm apart near the center of the pattern. When the laser is replaced by a small laser pointer, the fringes are 5.14 mm apart. What is the wavelength of the light produced by the laser pointer?

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Huyền Thanh 4 years 2021-07-20T13:13:39+00:00 1 Answers 222 views 0

Answers ( )

  1. thienan
    -1
    2021-07-20T13:15:03+00:00
    Reply

    Given Information:  

    Wavelength of the red laser = λr = 632.8 nm

    Distance between bright fringes due to red laser = yr = 5 mm

    Distance between bright fringes due to laser pointer = yp = 5.14 mm

    Required Information:  

    Wavelength of the laser pointer = λp = ?

    Answer:

    Wavelength of the laser pointer = λp = ?

    Explanation:

    The wavelength of the monochromatic light can be found using young’s double slits formula,

    y = Dλ/d  

    y/λ = D/d

    Where

    λ is the wavelength

    y is the distance between bright fringes.

    d is the double slit separation distance

    D is the distance from the slits to the screen

    For the red laser,

    yr/λr = D/d

    For the laser pointer,

    yp/λp = D/d

    Equating both equations yields,

    yr/λr = yp/λp

    Re-arrange for λp

    λp = yp*λr/yr

    λp =  (5*632.8)/5.14

    λp = 615.56 nm

    Therefore, the wavelength of the small laser pointer is 615.56 nm.

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