Test #2: Q6  [ENDORSED]


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Gabi Landes 1-H
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Joined: Thu Feb 22, 2018 3:00 am

Test #2: Q6

Postby Gabi Landes 1-H » Sun Apr 29, 2018 11:48 am

I got the second part of this question incorrect, I am assuming because of an accident when inputting the numbers into my calculator.
I have re-done the problem below and just want to make sure I am on the right track.

Q6. Microwave ovens use microwave electromagnetic radiation to cause vibrations within the molecules in food causing it to heat it up. Microwave radiation has a frequency of about 3x10^9 Hz. Determine the energy, in J, and the wavelength, in nm, of a microwave.

E=hv
E=(6.62608x10^-34 J*s)(3x10^9 s^-1)
E=2x10^-24 J

=c/v (from c=v)
= (2.99792x10^8 m*s^-1)/(3x10^9 s^-1)x(1 nm)/10^-9 m)
=9.99306667x10^-7 nm
= 10x10^-7 nm

FizaBaloch1J
Posts: 41
Joined: Fri Apr 06, 2018 11:01 am

Re: Test #2: Q6

Postby FizaBaloch1J » Sun Apr 29, 2018 2:52 pm

When I did this problem to find wavelength I used wavelength= ch/E instead.

Megan Potter 1G
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Re: Test #2: Q6  [ENDORSED]

Postby Megan Potter 1G » Sun Apr 29, 2018 4:04 pm

I also used wavelength=hc/E, but the way you do it works too. With rounding the answer is 10 x 10^7 (positive exponent of 7, not negative, because there's 10^9 nanometers in one meter)

Elena 1H
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Re: Test #2: Q6

Postby Elena 1H » Sun Apr 29, 2018 5:24 pm

I initially used the derived equation λ=hc/E but I realized it was easier to just use λ=c/v because all the values are given to you, but yes you are on the right track

Emely Reyna 1F
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Re: Test #2: Q6

Postby Emely Reyna 1F » Sun Apr 29, 2018 7:10 pm

I also used both E=hv and wavelength= c/v and came up with the same answer but using wavelength= hc/E is quicker and would result in less calculator error.

Myles Chang 1B
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Re: Test #2: Q6

Postby Myles Chang 1B » Sun Apr 29, 2018 8:02 pm

I think this is most likely just a calculator error. You should get the same answer regardless of what equation you use.

Samantha Castro 1D
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Re: Test #2: Q6

Postby Samantha Castro 1D » Sun Apr 29, 2018 9:12 pm

In addition, I also used E=hv and wavelength=c/v and came up with the same answer. But also using wavelenght=hc/E can work as well.

Gabi Landes 1-H
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Re: Test #2: Q6

Postby Gabi Landes 1-H » Tue May 01, 2018 9:00 pm

Megan Potter 1G wrote:I also used wavelength=hc/E, but the way you do it works too. With rounding the answer is 10 x 10^7 (positive exponent of 7, not negative, because there's 10^9 nanometers in one meter)


If you don't mind explaining more, just so I can possibly understand, why would 10^9 nanometers in one meter make the answer positive?

Paywand Baghal
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Joined: Fri Apr 06, 2018 11:01 am

Re: Test #2: Q6

Postby Paywand Baghal » Wed May 02, 2018 5:32 pm

Gabi Landes 1-H wrote:
Megan Potter 1G wrote:I also used wavelength=hc/E, but the way you do it works too. With rounding the answer is 10 x 10^7 (positive exponent of 7, not negative, because there's 10^9 nanometers in one meter)


If you don't mind explaining more, just so I can possibly understand, why would 10^9 nanometers in one meter make the answer positive?


Yes if possible could you explain? I am pretty sure 1 x 10^-9 m is 1 nm not positive 9

Megan Potter 1G
Posts: 35
Joined: Fri Apr 06, 2018 11:04 am

Re: Test #2: Q6

Postby Megan Potter 1G » Thu May 03, 2018 10:31 pm

So if you solve the equation you get this:

Wavelength = {(6.626 x 10^-34)(2.998 x 10^8)}/(1.99 x 10^-24)
wavelength = .099821 meters

there are 10^9 nanometers in one meter (nanometers are smaller so it makes sense that there should be a ton of them to make one meter)

using dimensional analysis to convert:
.099821 meters x (10^9 nm)/1m = 9.982 x 10^7 nm as the wavelength

hope this helps! let me know if there's something else I can explain
Last edited by Megan Potter 1G on Thu May 03, 2018 10:33 pm, edited 1 time in total.

Megan Potter 1G
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Joined: Fri Apr 06, 2018 11:04 am

Re: Test #2: Q6

Postby Megan Potter 1G » Thu May 03, 2018 10:32 pm

Paywand Baghal wrote:
Gabi Landes 1-H wrote:
Megan Potter 1G wrote:I also used wavelength=hc/E, but the way you do it works too. With rounding the answer is 10 x 10^7 (positive exponent of 7, not negative, because there's 10^9 nanometers in one meter)


If you don't mind explaining more, just so I can possibly understand, why would 10^9 nanometers in one meter make the answer positive?


Yes if possible could you explain? I am pretty sure 1 x 10^-9 m is 1 nm not positive 9



see my explanation above but yes you are right, 1x10^-9 m = 1nm, so 1x10^9 nm=1 m :)


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