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Chapter 38: Q 9 (page 1113)

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

Expert verified

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

01

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.

02

Step 2. Part a)

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

03

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.

04

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.

05

Step 5. Part d)

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

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Most popular questions from this chapter

FIGURE Q38.12 shows the energy-level diagram of Element X.

a. What is the ionization energy of Element X?

b. An atom in the ground state absorbs a photon, then emits a photon with a wavelength of 1240 nm. What was the energy of the photon that was absorbed?

c. An atom in the ground state has a collision with an electron, then emits a photon with a wavelength of 1240 nm. What conclusion can you draw about the initial kinetic energy of the electron?

A 100Wincandescent lightbulb emits about 5Wof visible light. (The other 95Ware emitted as infrared radiation or lost as heat to the surroundings.) The average wavelength of the visible light is about 600nm, so make the simplifying assumption that all the light has this wavelength. How many visible-light photons does the bulb emit per second?

a. Explain why the graphs of Figure 38.3 are mostly horizontal for ∆V > 0.

b. Explain why photoelectrons are ejected from the cathode with a range of kinetic energies, rather than all electrons having the same kinetic energy.

c. Explain the reasoning by which we claim that the stopping potential Vstop indicates the maximum kinetic energy of the electrons

Potassium and gold cathodes are used in a photoelectric effect experiment. For each cathode, find:

a) The threshold frequency.

b) The threshold wavelength.

c) The maximum photoelectron ejection speed if the light has a wavelength of 220 nm.

d) The stopping potential if the wavelength is 220 nm

Draw an energy-level diagram, similar to Figure 38.21, for the He+ion. On your diagram:

a. Show the first five energy levels. Label each with the values of n andEn

b. Show the ionization limit.

c. Show all possible emission transitions from the n = 4 energy level.

d. Calculate the wavelengths (in nm) for each of the transitions in part c and show them alongside the appropriate arrow.
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