Question

FIGURE Q38.9 is a simulation of the electrons detected behind two closely spaced slits. Each bright dot represents one electron. How will this pattern change if

a. The electron-beam intensity is increased?

b. The electron speed is reduced?

c. The electrons are replaced by neutrons?

d. The left slit is closed?

Your answers should consider the number of dots on the screen and the spacing, width, and positions of the fringes.

Short answer

a) Number of dots will increase.

b) More spread out fringes with the same number of dots in each fringe will be observed.

c) The fringes will be narrower and closer together.

d) Pattern becomes a single slit diffraction pattern.

Step-by-step solution

Step 1. A figure showing the simulation of the electrons detected behind two closely spaced slits is given to us.

We need to find out the change in pattern under certain conditions.

Step 2. Part a)

The number of dots will Increase, but they will remain in the same width bands.

Step 3. Part b)

The wavelength increases when the speed is reduced, leading to wider, more spread out fringes with the same number of dots in each fringe.

Step 4. Part c)

As neutrons have more mass than electrons, they have more momentum when travelling at the same speed. Because a smaller wavelength is associated with more momentum, the fringes are narrower and closer together.

Step 5. Part d)

The pattern becomes a single slit diffraction pattern. The two-slit interference pattern is eliminated.