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Homework Help: Equation Help

  1. Nov 1, 2005 #1
    If a blue light has a wavelength of 550 x 10^-9 (550 nanometers), what is the frequency of the light?

    I've went over this again and again and yet I keep messing up somewhere...

    The equation is the speed of light = wavelength * frequency right?

    If I'm trying to find the frequency, the equation would be the speed of light / wavelength = frequency...am I still okay or have I already messed up?:rofl:

    Okay, if the speed of light in a vacuum (That right there confuses me already but I decided not to delve into it...I'm gettin' tired.:zzz: ) is 2.99792 * 10^8 and the wavelength is 550 * 10^-9...then I just need to fill in the equation.

    2.99792 * 10^8/550 * 10^-9 = frequency

    Aye, that's a complicated thing to solve...:surprised I'm getting no where near the choice answers...

    5.45 x 10^14
    3.568 E -7
    5.5 x 10^-7
    2.99 x 10^8


    I tried solving that thing about four different ways and still didn't get it right...:bugeye:
     
    Last edited: Nov 1, 2005
  2. jcsd
  3. Nov 1, 2005 #2

    siddharth

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    You are right till now.

    It's not complicated to solve. Are you using a calculator to solve this? If so, remember to put the brackets properly when you are dividing.
     
  4. Nov 1, 2005 #3

    Astronuc

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    Along the lines of what siddharth mentioned,

    try 2.99792/550 * 108/10-9= 0.00545 * 1017

    Be careful how one treats the base (powers of 10).

    Discussion of scientific notation - http://www.nyu.edu/pages/mathmol/textbook/scinot.html
     
  5. Nov 1, 2005 #4

    HallsofIvy

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    Actually, whoever choose those "distractors" was in a generous mood. Looking at the exponents pretty much gives the answer away.
     
  6. Nov 1, 2005 #5
    siddharth: Are you using a calculator to solve this? If so, remember to put the brackets properly when you are dividing.

    No, I tried but I kept getting "ERR: SYNTAX" and I'm guessing it had to do with the negative exponent. That's why I tried to solve it by hand.

    Astronuc: try 2.99792/550 * 108/10-9= 0.00545 * 10^17

    I believe that's one of the things I tried but I messed up the exponents. When dividing, I thought you were to subtract them...Oh wait, that'd still come to 17.:yuck: Wow, I can't believe I made such a goofy mistake.:rofl: Either way, that isn't one of the answers...

    HallsofIvy: Looking at the exponents pretty much gives the answer away.

    Aye, I figured this was a rather easy problem that I just wasn't getting for some odd reason...:shy:

    I think I'll start this one over and try again, hopefully I'm not missing something that'll mess me up.:smile:
     
  7. Nov 1, 2005 #6
    Never mind, got it...that was a stupid question.:blushing:
     
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