Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm currently struggling to understand the physics behind this question (purely because our lecture hasn't given us proper grounding in quantum mechanics). In a double slit experiment, you are given $\psi_1= A_1e^{-i(ky-wt)/\sqrt{1+y^2}}$ and $\psi_2 = A_2e^{-i(ky+\pi y-wt)/\sqrt{1+y^2}}$ where $A_1$ and $A_2$ are normalization constants to be determined. These state vectors represent the diffraction pattern that occurs at 2 separate vertical detectors as a light source hits a screen.

I'm asked to calculate intensity when: a) 2 slits are opened and a light source is used to detect which slit the electron goes through. b) 2 slits are open with no light source.

I found $A_1$ and $A_2$ to both equal $1/\pi$ and to get intensity I know I have to superposition them and square the sum so intensity = $\psi_1^2 + \psi_2^2+2\psi_1\psi_2$. However I don't know what it means by the options a) and b) or if I am to get a single value for the intensity or is it to be in respect of $y$ and $t$. I would really appreciate it if someone could take the time to explain to me what it is I am meant to do.

share|cite|improve this question
Check if I formatted correctly the equations. – Ignacio Vergara Kausel Oct 20 '13 at 1:13
I would read the cases (a) and (b) again very carefully and think about what you're instructor has told you about QM. Draw it out on a piece of paper and go step by step. What is meaningful here? What did my lecturer say again? I think it is important for you to figure it out. – Derek E Oct 20 '13 at 2:27

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.