Dual Nature of Matter & Radiation - Notes Class 12 Notes | EduRev

Class 12 : Dual Nature of Matter & Radiation - Notes Class 12 Notes | EduRev

 Page 1


PHOTOELECTRIC EFFECT AND
DUAL NATURE OF MATTER AND RADIATIONS
1. Photons
2. Photoelectric Effect
3. Experimental Set-up to study Photoelectric Effect
4. Effect of Intensity, Frequency, Potential on P.E. Current
5. Graphical representation of variation of P.E. Current
6. Laws of Photoelectric Effect
7. Einstein’s Photoelectric Equation
8. Verification of Laws of Photoelectric Effect based on Einstein’s 
Photoelectric Equation
9. Application of Photoelectric Effect
10.Matter Waves and de Broglie wavelength
11.Davission & Germer Experiment
Page 2


PHOTOELECTRIC EFFECT AND
DUAL NATURE OF MATTER AND RADIATIONS
1. Photons
2. Photoelectric Effect
3. Experimental Set-up to study Photoelectric Effect
4. Effect of Intensity, Frequency, Potential on P.E. Current
5. Graphical representation of variation of P.E. Current
6. Laws of Photoelectric Effect
7. Einstein’s Photoelectric Equation
8. Verification of Laws of Photoelectric Effect based on Einstein’s 
Photoelectric Equation
9. Application of Photoelectric Effect
10.Matter Waves and de Broglie wavelength
11.Davission & Germer Experiment
Photon:
A packet or bundle of energy is called a photon.  
Energy of a photon is
E =  h? =
hc
?
where  h is the Planck’s constant, ? is the frequency of the 
radiation or photon, c is the speed of light (e.m. wave) and ? is 
the wavelength.
Properties of photons:
i) A photon travels at a speed of light c in vacuum. (i.e. 3 x 10
-8
m/s)
ii) It has zero rest mass. i.e. the photon can not exist at rest.  
iii) The kinetic mass of a photon is, 
m =
h
c?
E
c
2
=
iv) The momentum of a photon is,
p =
h
?
E
c
=
v) Photons travel in a straight line.
vi) Energy of a photon depends upon frequency of the photon; so the 
energy of the photon does not change when photon travels from one 
medium to another.
Page 3


PHOTOELECTRIC EFFECT AND
DUAL NATURE OF MATTER AND RADIATIONS
1. Photons
2. Photoelectric Effect
3. Experimental Set-up to study Photoelectric Effect
4. Effect of Intensity, Frequency, Potential on P.E. Current
5. Graphical representation of variation of P.E. Current
6. Laws of Photoelectric Effect
7. Einstein’s Photoelectric Equation
8. Verification of Laws of Photoelectric Effect based on Einstein’s 
Photoelectric Equation
9. Application of Photoelectric Effect
10.Matter Waves and de Broglie wavelength
11.Davission & Germer Experiment
Photon:
A packet or bundle of energy is called a photon.  
Energy of a photon is
E =  h? =
hc
?
where  h is the Planck’s constant, ? is the frequency of the 
radiation or photon, c is the speed of light (e.m. wave) and ? is 
the wavelength.
Properties of photons:
i) A photon travels at a speed of light c in vacuum. (i.e. 3 x 10
-8
m/s)
ii) It has zero rest mass. i.e. the photon can not exist at rest.  
iii) The kinetic mass of a photon is, 
m =
h
c?
E
c
2
=
iv) The momentum of a photon is,
p =
h
?
E
c
=
v) Photons travel in a straight line.
vi) Energy of a photon depends upon frequency of the photon; so the 
energy of the photon does not change when photon travels from one 
medium to another.
vii) Wavelength of the photon changes in different media; so, velocity of  
a photon is different in different media.
viii) Photons are electrically neutral.
ix)   Photons may show diffraction under given conditions.
x)    Photons are not deviated by magnetic and electric fields.
Photoelectric Effect:
The phenomenon of emission of electrons from mainly metal surfaces 
exposed to light energy (X – rays, ? – rays, UV rays, Visible light and even 
Infra Red rays) of suitable frequency is known as photoelectric effect.
The electrons emitted by this effect are called photoelectrons.                      
The current constituted by photoelectrons is known as photoelectric current.
Note:  Non metals also show photoelectric effect.  Liquids and gases also 
show this effect but to limited extent.
UV
Metals Metals other than Alkali Metals Alkali Metals
Visible light
No photoelectrons
Photoelectrons
Photoelectrons
Visible light
Page 4


PHOTOELECTRIC EFFECT AND
DUAL NATURE OF MATTER AND RADIATIONS
1. Photons
2. Photoelectric Effect
3. Experimental Set-up to study Photoelectric Effect
4. Effect of Intensity, Frequency, Potential on P.E. Current
5. Graphical representation of variation of P.E. Current
6. Laws of Photoelectric Effect
7. Einstein’s Photoelectric Equation
8. Verification of Laws of Photoelectric Effect based on Einstein’s 
Photoelectric Equation
9. Application of Photoelectric Effect
10.Matter Waves and de Broglie wavelength
11.Davission & Germer Experiment
Photon:
A packet or bundle of energy is called a photon.  
Energy of a photon is
E =  h? =
hc
?
where  h is the Planck’s constant, ? is the frequency of the 
radiation or photon, c is the speed of light (e.m. wave) and ? is 
the wavelength.
Properties of photons:
i) A photon travels at a speed of light c in vacuum. (i.e. 3 x 10
-8
m/s)
ii) It has zero rest mass. i.e. the photon can not exist at rest.  
iii) The kinetic mass of a photon is, 
m =
h
c?
E
c
2
=
iv) The momentum of a photon is,
p =
h
?
E
c
=
v) Photons travel in a straight line.
vi) Energy of a photon depends upon frequency of the photon; so the 
energy of the photon does not change when photon travels from one 
medium to another.
vii) Wavelength of the photon changes in different media; so, velocity of  
a photon is different in different media.
viii) Photons are electrically neutral.
ix)   Photons may show diffraction under given conditions.
x)    Photons are not deviated by magnetic and electric fields.
Photoelectric Effect:
The phenomenon of emission of electrons from mainly metal surfaces 
exposed to light energy (X – rays, ? – rays, UV rays, Visible light and even 
Infra Red rays) of suitable frequency is known as photoelectric effect.
The electrons emitted by this effect are called photoelectrons.                      
The current constituted by photoelectrons is known as photoelectric current.
Note:  Non metals also show photoelectric effect.  Liquids and gases also 
show this effect but to limited extent.
UV
Metals Metals other than Alkali Metals Alkali Metals
Visible light
No photoelectrons
Photoelectrons
Photoelectrons
Visible light
Experimental Set-up to study Photoelectric Effect:
Glass transmits only visible and infra-red lights but not UV light.
Quartz transmits UV light.
When light of suitable frequency falls on the metallic cathode, photoelectrons 
are emitted.  These photoelectrons are attracted towards the +ve anode and 
hence photoelectric current is constituted.
UV light
K
? ?
V
+
µA
+
C A
W
C – Metallic cathode
A – Metallic Anode
W – Quartz Window
- Photoelectron
Page 5


PHOTOELECTRIC EFFECT AND
DUAL NATURE OF MATTER AND RADIATIONS
1. Photons
2. Photoelectric Effect
3. Experimental Set-up to study Photoelectric Effect
4. Effect of Intensity, Frequency, Potential on P.E. Current
5. Graphical representation of variation of P.E. Current
6. Laws of Photoelectric Effect
7. Einstein’s Photoelectric Equation
8. Verification of Laws of Photoelectric Effect based on Einstein’s 
Photoelectric Equation
9. Application of Photoelectric Effect
10.Matter Waves and de Broglie wavelength
11.Davission & Germer Experiment
Photon:
A packet or bundle of energy is called a photon.  
Energy of a photon is
E =  h? =
hc
?
where  h is the Planck’s constant, ? is the frequency of the 
radiation or photon, c is the speed of light (e.m. wave) and ? is 
the wavelength.
Properties of photons:
i) A photon travels at a speed of light c in vacuum. (i.e. 3 x 10
-8
m/s)
ii) It has zero rest mass. i.e. the photon can not exist at rest.  
iii) The kinetic mass of a photon is, 
m =
h
c?
E
c
2
=
iv) The momentum of a photon is,
p =
h
?
E
c
=
v) Photons travel in a straight line.
vi) Energy of a photon depends upon frequency of the photon; so the 
energy of the photon does not change when photon travels from one 
medium to another.
vii) Wavelength of the photon changes in different media; so, velocity of  
a photon is different in different media.
viii) Photons are electrically neutral.
ix)   Photons may show diffraction under given conditions.
x)    Photons are not deviated by magnetic and electric fields.
Photoelectric Effect:
The phenomenon of emission of electrons from mainly metal surfaces 
exposed to light energy (X – rays, ? – rays, UV rays, Visible light and even 
Infra Red rays) of suitable frequency is known as photoelectric effect.
The electrons emitted by this effect are called photoelectrons.                      
The current constituted by photoelectrons is known as photoelectric current.
Note:  Non metals also show photoelectric effect.  Liquids and gases also 
show this effect but to limited extent.
UV
Metals Metals other than Alkali Metals Alkali Metals
Visible light
No photoelectrons
Photoelectrons
Photoelectrons
Visible light
Experimental Set-up to study Photoelectric Effect:
Glass transmits only visible and infra-red lights but not UV light.
Quartz transmits UV light.
When light of suitable frequency falls on the metallic cathode, photoelectrons 
are emitted.  These photoelectrons are attracted towards the +ve anode and 
hence photoelectric current is constituted.
UV light
K
? ?
V
+
µA
+
C A
W
C – Metallic cathode
A – Metallic Anode
W – Quartz Window
- Photoelectron
1)  Effect of Intensity of Incident Light on Photoelectric Current:
For a fixed frequency, the photoelectric current 
increases linearly with increase in intensity of 
incident light.
2)  Effect of Potential on Photoelectric Current:
For a fixed frequency and intensity of 
incident light, the photoelectric 
current increases with increase in 
+ve potential applied to the anode.
When all the photoelectrons reach 
the plate A, current becomes 
maximum and is known as saturation 
current.
I 
µA
Intensity (L)
0
0
Saturation Current
L
1
L
2
L
2 
> L
1
This shows that even in the absence of accelerating potential, a few 
photoelectrons manage to reach the plate on their own due to their K.E.
When –ve potential is applied to the plate A w.r.t. C, photoelectric current 
becomes zero at a particular value of –ve potential called stopping potential
or cut-off potential.
When the potential is decreased, 
the current decreases but does not 
become zero at zero potential.
Intensity of incident light does not affect the stopping potential.
I 
µA
+
Potential of A  (V) V
S
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