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Question on themal conduction and a quick question on spectrometer

  1. Aug 16, 2009 #1
    This problem has been SOLVED.thx.





    Question 1

    1. The problem statement, all variables and given/known data
    1)The temperature of an ice layer,of thickness 50m, is -50 deg.C.If the ice layer continues to grow,find the timetaken for it to grow by another 1mm.
    Temperature at the bottom of ice layer is 0 deg.C

    2)Calculate the minimum rate at which heat should be provided per unit area of the ice layer by warm water currents beneath to stop growth of the above mentioned layer at 50m

    3)If the warm currents provide heat at the rate of 0.5Wm-2 for 2 days,what would be the thickness of the 50m icelayer after 2 days

    2. Relevant equations
    Q/t = kA (t1-t2)/d
    t=temperature
    d=thickness
    k=thermal conductivity of ice = 2W/m2


    Q/t=mL/t

    L=latent heat of fusion of ice at 0 deg.C = 3.6*105


    3. The attempt at a solution

    1) mL/t = kA (t1-t2)/d
    A*1*10-3*900*3.6*105/t = 2*A*50/50 ?
    I think the above equation is correct,but if the question says the thickness of the icelayer has grown by,say 40cm,then d would have to be 40 ?
    or is it (40+50)/2 ? I can't quite remember which our teacher said.

    2) Q/tA = k (t1-t2)/d
    =2*50/50

    3)I don't know

    Question 2 - spectrometer

    a )At the minimum deviation position,the scale reading of the spectrometer is 3degrees 16'.
    If the scale reading of the spectrometer when the collimater and the telescope are kept in the same straight line ,is 223deg 46'.
    Calculate the angle of minimum deviation ?

    I'm not sure if I should subtract 3degrees 16' from 223deg 46' directly,or first subtract 223deg 46' from 360,then add 3degrees 16' ?


    b) The images of the slit due to the colours yellow,blue,red and green light are different.
    Draw the relative positions of the images due to the 4 colours and also due to white light .

    I've never done the spectrometer experiment in class ,so I'm not sure how the images would appear.
    I know that the images of the slit for yellow and white light would appear symmetrical on the crosswires but for red,blue and green ?
     
    Last edited: Aug 17, 2009
  2. jcsd
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