Electrons and energy levels (3)

Question 1

Electromagnetic waves

Answer 1

transverse waves with a range of wavelengths, all of which travel at the speed 3 x 108 ms-1 in a vacuum.

Question 2

Diffraction

Answer 2

occurs when waves spread through a gap or around an obstacle. The wave front is more curved when the wavelength is about the same size as the gap, and diffraction is greatest.

Question 3

Threshold frequency

Answer 3

the minimum frequency of light required to cause the photoelectric effect.

Question 4

Intensity

Answer 4

is rate of energy transfer per unit area.

Question 5

Photoelectron

Answer 5

an electron emitted during the photoelectric effect.

Question 6

Threshold energy

Answer 6

is the minimum amount of energy required to cause the photoelectric effect.

Question 7

Potential well

Answer 7

is a model to help us understand why electrons require energy to remove them from a metal. An electron has its least potential energy in the potential well.

Question 8

Work function

Answer 8

is the least energy needed to release a photoelectron from a material. This equals the threshold energy.

Question 9

Semiconductor

Answer 9

is a material with conductivity between a metal and an insulator.

Question 10

De Broglie wavelength

Answer 10

the de Broglie wavelength for a particle is the Planck constant divided by a particle’s momentum; it represents the wavelength of a moving particle, or
λ=h/p

Question 11

Wave-particle duality

Answer 11

is the idea that matter and radiation can be described best by sometimes using a wave model and sometimes using a particle model.