Using Plank's constant...

[cougarblue84]

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[SIZE=+1]The value of Plank’s constant is 6.63 * 10-34 J * s. The velocity of light is 3.0 * 108 m * s-1. Which value is closest to the wave length in nanometers of a quantum of light with frequency of 8 * 1015 sec-1?[/SIZE]
[SIZE=+1] A. 3 * 107[/SIZE]
[SIZE=+1] B. 4 * 101[/SIZE]
[SIZE=+1] C. 5 * 10-18[/SIZE]
[SIZE=+1] D. 2 * 10-25[/SIZE]
[SIZE=+1] E. 1 * 10-25[/SIZE]

Correct answer is listed as C. Anyone know how you'd go about solving this problem? I've looked up the formula, but I'm not sure how to apply this question to the formula...

 

[mddang]

[SIZE=+1]The value of Plank’s constant is 6.63 * 10-34 J * s. The velocity of light is 3.0 * 108 m * s-1. Which value is closest to the wave length in nanometers of a quantum of light with frequency of 8 * 1015 sec-1?[/SIZE]
[SIZE=+1] A. 3 * 107[/SIZE]
[SIZE=+1] B. 4 * 101[/SIZE]
[SIZE=+1] C. 5 * 10-18[/SIZE]
[SIZE=+1] D. 2 * 10-25[/SIZE]
[SIZE=+1] E. 1 * 10-25[/SIZE]

Correct answer is listed as C. Anyone know how you'd go about solving this problem? I've looked up the formula, but I'm not sure how to apply this question to the formula...

For this particular problem, they give you the frequency of the light, so you don't need Planck's constant.


Now if they were to say 'The energy of a photon of light is 5,000J (or any number...). What is the wavelength of the light?'


First thing you would do is to find the frequency using Planck's constant.

frequency = 5,000J/(6.63*10^-34 J*s)


Now that you have the frequency, you can find the wavelength by dividing the speed of light by the frequency.

3.00x10^8m/s/(5,000J/(6.63*10^-34 J*s)) = whatever it equals



Dimensional analysis is the easiest way to work things out. Just look at the units of what is given and use them to get to what you are trying to find.