Quantum

what is Photoelectric effect?

Where one free electron on a metal's surface absorbs energy from one photon

What is the emitted electron called?

Photoelectron

What happens if the frequency is enough (>threshold frequency) + the energy is enough (>work function)?

The electron is released

what is 1eV equivalent to in joules?

1\.6x10^-19 J

Unit for electron energy ?

Electron volt (eV)

What is 1eV (definition) ?

The energy transferred when an electron travels through a potential difference of 1 volt.

h x f =

Φ + Ek (max)

What is Work function ?

Minimum energy to remove electron from the metal's surface

What is Threshold frequency?

Minimum frequency needed to remove an electron from the metals surface

At the minimum threshold to free an electron: kinetic energy = what ?

0

The gradient of a KE:f graph = what ?

Planck's constant

How can a circuit be used to find the maximum kinetic energy for photoelectrons?

• A potential difference is increased in the opposite direction to the way the electrons are moving.

• When the electrons just fail to reach the anode, the stopping potential has been reached.

• Ek(max) = eV(stop)

What is the excess energy in photoelectric effect called ?

kinetic energy

What is Excitation?

Electrons moving up energy levels

What is De-excitation ?

Electrons moving down energy levels

What does Change in Energy = ?

Planck's constant x frequency

What is Ionisation ?

The electron escapes completely from the top energy level of the atom

What is Ionisation energy ?

The minimum energy needed to completely free an electron from an atom

How else can we ionise gas atoms?

By applying a voltage

How do fluorescent lights work?

They generate UV radiation which is absorbed (mercury vapour) and re emitted as visible light by a layer of phosphorus inside the bulb

(De Broglie) wavelength = ?

Planck's constant / momentum 

Electrons interfere in a ____ _________ pattern.

Wave interface

Greater momentum (from faster electrons) means ?

Smaller de Broglie wavelength