# Chapter 4 - Particles of Light [Complete] Flashcards

What is the photoelectric effect?

The ability for a negatively charged material, such as a negatively charged zinc plate, to release electrons if they receive a wavelength of light that is above their threshold frequency

What is a photoelectron?

An electron that is emitted during or as a result of the photoelectric effect

What is the value for Planck’s constant?

6.6 x 10^-34

Does UV have a higher or lower frequency than visible light?

Higher

What is the kinetic energy of a released photoelectron dependent on?

The frequency of the incident photon

What is the equation linking together Planck’s constant, frequency and energy?

Energy = frequency x Planck’s constant

What is intensity?

The rate of energy transfer per unit area

Explain the potential well model.

- Electrons are visualised as being within a well of energy when they are embedded in an atom or ion, they need a greater, set amount of energy to get out the attraction of the nucleus // - Photons are able to transfer energy to electrons by colliding with them // - Work function is overcome and remainder is kinetic energy // - Person cannot get out of the hole with two smaller jumps - akin to electron cannot get out with two smaller below threshold photons // - E = hf

What is the work function?

The least energy needed to release a photoelectron from a material. It is the same as the threshold energy

What is Einstein’s photoelectric equation?

hf = work function + 1/2mv[max]^2

What is the work function below which the photoelectrons can be released by visible light?

3.1 eV

What is the work function below which the photoelectrons can be released by infrared light?

1.77 eV

How is stopping potential calculated and what does it tell you?

Stopping potential is calculated by using a photoelectric cell in which there is a positively charged and negatively charged plate on each side. When light strike the surface of the positively charged plate, the electrons are released and start to move towards the opposite plate. However, since this plate is negatively charged, they slow down and come to a stop before they hit it. This stopping potential represents the kinetic energy of the electrons, and is calculated using the equation 1/2mv^2 = eV

What did De Broglie propose? What are the equations he formulated?

That particles, like electrons, could behave like waves and that the equation lamda = h/p where lamda is wavelength, h is Planck’s constant, and p is the electron’s momentum could calculate this wavelength, the other version of this is lamda = Planck’s constant / mass x velocity

What condition is in play when diffraction is the greatest it can be?

When the wavelength of the particle/wave is the same/approximately the same as the gap it is passing through