Wavelength, Frequency, and Planck's Constantby Soaring Crane Tags: constant, frequency, planck, wavelength 

#1
Nov305, 03:08 PM

P: 483

1) What is the wavelength (in meters) of an electromagnetic wave of frequency 2812571875.00MHz?
Example: 1.11e5 LAMBDA = c/v =(3.00*10^8 m/s)/(2812571875.00MHz*10^6 Hz/MHz) = 1.07E7 m?? _________________________________________________________________ 2) What is the wavelength (in meters) of an electromagnetic wave of frequency 7084.00MHz? LAMBDA = c/v =(3.00*10^8 m/s)/(7084.00MHz*10^6 Hz/MHz) = 4.23E1 m?? _________________________________________________________________ 3) How much energy is carried by a mole of photons with frequency 704.00MHz? Give your answer in kilojoules per mole, Example: 1.11e5 Careful with your conventions. E = hv =(6.626*10^34)*(704.00MHz*10^6 Hz/MHz) = 4.665E25 J 4.665E25 J(1 kJ/10^3 J)* (6.02*10^23 photons/1mol) = 2.81E4 kJ/mol?? _________________________________________________________________ Did I express my answers with the right significant digits and calculations? Thanks. 



#2
Nov305, 03:53 PM

PF Gold
P: 7,125

Yes, the significant digits look correct and the calculations seem correct although I don't have a calculator around at the moment.




#3
Nov305, 05:03 PM

Mentor
P: 7,290

You are given a lot of signifiant digits in your problem, why did you only use 3 for c? Is that c to 3 digits? There are about 8 digits of c available, why not use them?




#4
Nov305, 05:06 PM

PF Gold
P: 7,125

Wavelength, Frequency, and Planck's Constant 



#5
Nov305, 06:06 PM

Sci Advisor
HW Helper
P: 1,327

You should have (1 kJ/10^3J), using your equation as written, you would get 281 kJ/mol 



#6
Nov405, 05:17 AM

P: 483

For #2, it is 4.23E2 m?
For the constant c, my textbook gives the value in 8 decimal places, but it says that it is mostly rounded off to 3.00*10^8 and it uses this rounded off version in examples. 



#7
Nov405, 05:21 PM

Sci Advisor
HW Helper
P: 1,327

Nice job on #2 !! Try solving your questions, more than one way. Then you will be able to catch things like this on your own.
If they use the rounded off version of c in their examples, for practical purposes, you probably can use it as well. If you're in doubt, ask your teacher first before handing in those questions.. 


Register to reply 
Related Discussions  
Planck's Constant  Quantum Physics  20  
The determination of frequency v from Planck's formula  Advanced Physics Homework  0  
Planck's constant  General Discussion  11  
Question about Planck's constant  General Physics  2  
Which one is the Planck's constant?  Quantum Physics  11 