OPTICAL PHENOMENA
Photoelectric Effect
The process whereby electrons are ejected from a metal surface
when light of suitable frequency is incident on that surface
Photon Energy
The energy of a photon of light can be calculated as follows:
E = hf
E = hc
h= Planck’s constant (6,63 x 10 )
-34
Measured in Joules
Threshold Frequency
The minimum frequency of light needed to emit electrons from a
certain metal surface (f0)
Work Function
The work function of a metal is the minimum energy that an
electron in the metal needs to be emitted from the metal surface
(W0)
Electron Energy
If the energy of the photons exceed the work function, the excess
energy is transferred to the liberated electron in the form of kinetic
energy
The kinetic energy of the electron can be determined by:
E = W0+Ek (max)
W0 =hf0
Ek (max) = 12m(vmax)2
Significance of the Photoelectric Effect
The wave nature of light can explain the phenomena of reflection,
refraction and interference of light
The photoelectric effect is experimental evidence that shows that
light has particle properties
Light is thus said to have a dual nature: it has both wave and
particle properties
Intensity & Frequency
Increasing the intensity (brightness) of the light means that there
are more photos with the same frequency
Photoelectric Effect
The process whereby electrons are ejected from a metal surface
when light of suitable frequency is incident on that surface
Photon Energy
The energy of a photon of light can be calculated as follows:
E = hf
E = hc
h= Planck’s constant (6,63 x 10 )
-34
Measured in Joules
Threshold Frequency
The minimum frequency of light needed to emit electrons from a
certain metal surface (f0)
Work Function
The work function of a metal is the minimum energy that an
electron in the metal needs to be emitted from the metal surface
(W0)
Electron Energy
If the energy of the photons exceed the work function, the excess
energy is transferred to the liberated electron in the form of kinetic
energy
The kinetic energy of the electron can be determined by:
E = W0+Ek (max)
W0 =hf0
Ek (max) = 12m(vmax)2
Significance of the Photoelectric Effect
The wave nature of light can explain the phenomena of reflection,
refraction and interference of light
The photoelectric effect is experimental evidence that shows that
light has particle properties
Light is thus said to have a dual nature: it has both wave and
particle properties
Intensity & Frequency
Increasing the intensity (brightness) of the light means that there
are more photos with the same frequency
