# Double Slit question

1. May 19, 2006

### physics_06er

Hello

Could someone please help me with this question,,I have no idea how to work it out and have looked through my text book/notes and arrrr still can't do it...

A beam of photons encounters a double slit that has a separation distance d = 34.0 μm. Note: the diagram is not drawn to scale...(the diagram just shows a slit with a detector array 'x' meters away)

a)...if a single photon in the beam has an energy of 16.81x10^-19J what is it's energy in eV?

I calculated that to be 10.5eV but then its the next one I cant do as I have no other info. besides seperation distance and energy!!!

b) What is it's wavelength?
???????

Any help would be much appreciated
Thank you
physics_06er

2. May 19, 2006

### maverick280857

You have to show your work here first.

The two questions are very easy. Go through your Modern Physics textbook/course notes again...you're missing something.

3. May 19, 2006

### Chi Meson

I think this is enough of a hint: there was a guy named Max Planck...

4. May 19, 2006

### Hootenanny

Staff Emeritus
:rofl: :rofl: :rofl: And he lived in a land far far away.... :tongue2:

~H

5. May 19, 2006

### Chi Meson

Then one day, the morning after the ultraviolet catastrophe erupted...
...
nah!

Sorry, back to the thread. What is the thing Planck is most remembered for?

6. May 19, 2006

### Hootenanny

Staff Emeritus
Yes, I think this thread has become a little tangental. We should wait for the OP to return before we continue our story

~H

7. May 19, 2006

### physics_06er

Hi there

Thanks for the help

so I just found Freq using E=hf and then wavelength using c=f.lamda coming up with 1.18e-7m

Thanks again
physics_06er

...You guys can carry on your story if you wish

8. May 20, 2006

### physics_06er

Hello there...so I worked out how to to the angle question...however can someone pls check my working...by the way I made a mistake in my first post the seperation distance is 38.0micrometres

...so to find the freq. i used E/h ..16.81e-19/6.63e-19=2.535444947Hz then I went 3e8/2.535444947 and got 118322427.1 (its in meters right)..well the answer says 0.118nm??? What have I done wrong...

Next for the angle question i used dsintheta=(m+0.5)lamda and got an angle of 0.089...however this is when I use the answer they have given me...someone please tell me where I have gone wrong?

Last edited: May 20, 2006
9. May 20, 2006

### physics_06er

seems my angle question was deleted...but the question was if the detector array is placed 3.0m behind the double slit determine:...the angle m=0 destructive interference which is the one I have answered above---and also this one I hav NO idea how to do...determine the distance above the center of the interference pattern..I dont even know what they are asking?

10. May 23, 2006

### tyco05

re-check your value for h.... I haven't done the calculations, but it should put you in the right ball park