3D.3 Electron diffraction and interference

Question 1

What does electron diffraction demonstrate?

Answer 1

That electrons behave as waves.

Question 2

Why does diffraction prove electrons behave as waves?

Answer 2

Because diffraction is a wave phenomenon.

Question 3

Which experiment demonstrated electron diffraction?

Answer 3

The Davisson–Germer experiment.

Question 4

What did the Davisson–Germer experiment show?

Answer 4

Electrons diffract when reflected from a crystal lattice, producing an interference pattern.

Question 5

What pattern is produced in electron diffraction experiments?

Answer 5

A diffraction pattern of bright and dark regions.

Question 6

What did de Broglie propose about particles?

Answer 6

All particles have a wavelength.

Question 7

What equation gives the wavelength of a particle?

Answer 7

λ = h/p.

Question 8

What do the symbols represent in the de Broglie equation?

Answer 8

λ = wavelength, h = Planck’s constant, p = momentum.

Question 9

What is momentum in the de Broglie equation?

Answer 9

p = mv.

Question 10

Write the full de Broglie equation using velocity.

Answer 10

λ = h/mv.

Question 11

What experiment shows electrons can produce interference patterns?

Answer 11

The double-slit electron experiment.

Question 12

What happens when electrons pass through two slits?

Answer 12

They produce an interference pattern.

Question 13

What does electron interference demonstrate?

Answer 13

That electrons behave as waves.

Question 14

What does electron diffraction support?

Answer 14

Wave–particle duality.

Question 15

What does wave-particle duality mean?

Answer 15

Particles can behave as both waves and particles.

Question 16

Why are electron microscopes able to see very small objects?

Answer 16

Electrons have very short wavelengths.

Question 17

What determines the wavelength of electrons in a microscope?

Answer 17

The accelerating voltage.

Question 18

What happens to electron wavelength when accelerating voltage increases?

Answer 18

Wavelength decreases.

Question 19

Why does a smaller wavelength improve microscope resolution?

Answer 19

Because smaller wavelengths can resolve smaller objects.

Question 20

What instrument uses electron wave behaviour to produce high-resolution images?

Answer 20

The electron microscope.

Question 21

What key equation must be remembered for electron diffraction?

Answer 21

λ = h/p.