A-LEVEL PHYSICS: 2.5.5: Diffraction Effects of Momentum (SaveMyExams)

Question 1

when electrons pass through a slit similar in size to their de Broglie wavelength, they exhibit:

Answer 1

diffraction (a property of waves)

Question 2

the regular spacing of atoms in a crystalline solid acts as a ______, scattering the ______.
the observed diffraction pattern can be used to deduce the structure of crystal producing pattern

Answer 2

diffraction grating, electrons in a predictable manner

Question 3

high energy electrons have ______ and therefore can be used to…

Answer 3

shorter wavelength
look at the size of the nucleus of an atom

Question 4

momentum p=mv, so from de Broglie’s equation:

Answer 4

-smaller momentum —> longer wavelength

-larger momentum —> shorter wavelength

Question 5

speed of an electron can be increased by…

Answer 5

increasing the accelerating voltage

Question 6

if the electron speed (& therefore Ek) is increased: (2)

Answer 6

-wavelength of wave decreases (greater energy)

-diffraction rings will appear closer together

Question 7

the higher the Ek of the electron, the higher its momentum, hence…

Answer 7

shorter its de Broglie wavelength (greater energy —> shorter wavelength)

Question 8

radius of diffraction pattern depends on the wavelength: (2)

therefore:

Answer 8

-longer wavelength: more light spreads out, larger radius

-shorter wavelength: smaller radius produced

electrons with smaller momentum will produce more diffuse diffraction pattern