Question

126 Double slit interference: photons Photons are fired, one at a time toward a barrier that contains two slits. The diagram illustrates that prob- ability with which they arrive at various locations o a screen. The arrows indicate two locations, A and B, on the screen. a) A photon is fired toward the screen and it hits location B. The next photon is then fired to- ward the screen. Which of the following is true about the next photon to arrive on the screen? Explain your answer. i) The photon will definitely not arrive at A and will definitely not arrive at B. ii) The photon will definitely not arrive at A and will definitely arrive at B ii) The photon will definitely not arrive at A and might arrive at B. iv) The photon will definitely not arrive at B and will definitely arrive at A. v) The photon will definitely not arrive at B and might arrive at A. b) Which of the following modifications (select all that could be correct) could cause the next photon to arrive at A? Explain your answer. i) Increasing the intensity of light. ii) Decreasing the intensity of light. ili) Increasing the wavelength of light. iv) Decreasing the wavelength of light. v) Increasing the slit separation. vi) Decreasing the slit separation.

Answer 1

The intensity of the interference pattern at A is zero, that means that a photon will definitely not arrive at A, while it may or may not arrive at B (it has non vanishing probability to arrive at any point where intensity is non zero.)

(iii) is the correct answer.

(b) If we change the wavelength or slit width the intensity pattern will change and the point A will have non zero intensity. Therefore, a photon may arrive now at A. Hence, correct answers are (iii), (iv),(v),(vi).