Understand the the phenomenon of Photoelectric effect with the help of virtual lab and also learn about the conditions required for this phenomenon. Plot the graph between the observed quantities during performing this experiment. And calculate the value of Planck's Constant ,work function and cut-off frequency with the help of Graph.

1. PHOTO-ELECTRIC EFFECT
PHOTO-ELECTRIC EFFECT

2. AIM
To understand the phenomenon of Photoelectric effect.
To plot a graph connecting photocurrent and applied potential.
To plot a graph connecting kinetic energy and frequency.
To determine the Planck's constant from kinetic energy vs frequency graph.
To determine work function and cut-off frequency.

3. history of photoelectric effect
The photoelectric effect was first introduced by Franz Hallwachs in the year 1887 and
the experimental verification was done by Heinrich Rudolf Hertz.
Today, I'm demonstrate the photoelectric effect as a phenomenon which involves a
material absorbing electromagnetic radiation and releasing electrically charged
particles.
After continuous research in this field, the explanation for the photoelectric effect was
successfully explained by Albert Einstein.
For this excellent work, he was honoured with the Nobel prize in 1921.

4. WHAT IS THE PHOTO-ELECTRIC EFFECT
???

5. These ejected electrons are called photoelectrons.
The process through which photoelectrons are ejected from the surface of
the metal due to the action of light is commonly referred to as
photoemission.
The photoelectric effect is a phenomenon in which electrons are ejected from
the surface of a metal when light is incident on it.
It is important to note that the emission of photoelectrons and the kinetic
energy of the ejected photoelectrons is dependent on the frequency of the light
that is incident on the metal’s surface.

6. WHY DOES THE PHOTO-ELECTRIC EFFECT
OCCURS ???

7. The photoelectric effect occurs because the electrons at the surface of the
metal tend to absorb energy from the incident light and use it to
overcome the attractive forces that bind them to the metallic nuclei.
An illustration detailing the emission of photoelectrons as a result of the
photoelectric effect is shown below.
Metal Surface Electrons
Ejected-Electrons
Incident light

8. To be more precise, light incident on the surface of a metal in the
photoelectric effect causes electrons to be ejected. The electron ejected due to
the photoelectric effect is called a photoelectron and is denoted by e–.
The current produced as a result of the ejected electrons is called
photoelectric current.

9. Explanation of the Photoelectric Effect :
The photoelectric effect cannot be explained by considering light as a wave.
owever, this phenomenon can be explained by the particle nature of light, in which
light can be visualized as a stream of particles of electromagnetic energy. These
‘particles’ of light are called photons.
The energy held by a photon is related to the frequency of the light via Planck’s
equation:
E = h𝜈 = hc/λ
E denotes the energy of the photon
h is Planck’s constant
𝜈 denotes the frequency of the light
c is the speed of light (in a vacuum)
λ is the wavelength of the light
Where,

10. PHOTO-ELECTRIC EFFECT
Experimental arrangement

11. Conditions for Photoelectric Effect
Threshold Frequency :
It is the minimum frequency of the incident light or radiation that will
produce a photoelectric effect i.e. ejection of photoelectrons from a metal
surface.
If γ < γth, there will be no ejection of photoelectron and, therefore, no
photoelectric effect.
If γ = γth, photoelectrons are just ejected from the metal surface, in this case,
the kinetic energy of the electron is zero
If γ > γth, then photoelectrons will come out of the surface along with kinetic
energy
If γ = frequency of incident photon and γth= threshold frequency, then,

12. Conditions for Photoelectric Effect
Threshold Wavelength:
During the emission of electrons, a metal surface corresponding to the
greatest wavelength to incident light is known threshold wavelength.
If λ < λTh, then the photoelectric effect will take place and ejected electron
will possess kinetic energy.
If λ = λTh, then just photoelectric effect will take place and kinetic energy of
ejected photoelectron will be zero.
If λ > λTh, there will be no photoelectric effect.
For wavelengths above this threshold, there will be no photoelectron emission.
If λ = wavelength of the incident photon, then

13. Conditions for Photoelectric Effect
Work Function or Threshold Energy (Φ) :
It is the minimum quantity of energy which is required to remove an electron
to infinity from the surface of a given metal.
If E < Φ, no photoelectric effect will take place.
If E = Φ, just photoelectric effect will take place but the kinetic energy of ejected
photoelectron will be zero
If E > photoelectron will be zero
If E > Φ, the photoelectric effect will take place along with possession of the
kinetic energy by the ejected electron.
If E = energy of an incident photon, then

14. Conditions for Photoelectric Effect
Stopping potential (cut-off potential) :
Stopping potential or cut-off potential is defined as the required potential for
stopping the removal of an electron from a metal surface when the incident
light energy is greater than the work potential of the metal on which the
incident light is focused.
Stopping potential does not depend on the intensity of incident radiation. On
increasing intensity, the value of saturated current increases, whereas the
stopping potential remains unchanged.
For a given intensity of radiation, the stopping potential depends on the
frequency. Higher the frequency of incident light higher the value of stopping
potential.

15. SImULATION ON V-LAB
SImULATION ON V-LAB

17. For performing the simulation:
1. Select the material for studying photoelectric effect.
2. Select area of the material,wave-length,intensity of incident light.
3. Switch on the light source.
4. Measure the reverse current for various reverse voltages.
5. Plot the current-voltage graph and determine the threshold voltage.
6. Repeat the experiment by varying the intensity for a particular wavelength of
incident light.
7. Repeat the experiment by varying the wavelength for a particular intensity of the
incident light .

18. observations from simulator
observations from simulator

19. PHOTO-ELECTRIC EFFECT
observations
Table for applied voltage and current At- constant frequency and different intensities :
Material: Copper Area of plate: 0.5 cm^2
At; constant frequency: 2 x 10^15Hz.

20. Graph:

21. Graph:

22. PHOTO-ELECTRIC EFFECT
Area of plate: 0.5 cm^2
At; constant Intensity: 10W/m^2
observations
Material: Copper

23. Graph:

24. Graph:

25. PHOTO-ELECTRIC EFFECT
calculations
For Copper:
Calculation of Planck's constant
Slope of the graph = Planck's constant
We know that,
Δy
Δx
=
m =
ΔE
Δf
= Planck's constant
now,
(7.8 - 0.3) x 1.6 x 10
-19
h =
J
3 x 10 - 1.2 x 10 / sec
15 15
=
12
1.8
x 10
-34
J-sec. = 6.66 x 10
-34
J-sec.
h = 6.66 x 10
-34
J-sec.

26. PHOTO-ELECTRIC EFFECT
calculations
For Copper:
Calculation of Work Function
=
=
W hf - Ek
o
h c - E
=
λ
=
6.66 x 10 x 3 x 10
-34 8
100 x 10
-9
J-sec. m/sec.
m
- 7.8 eV
19.98 x 10
-19
1.6x 10
-19
- 7.8 eV
eV = (12.487 - 7.8)eV
Wo =
4.687 eV
=
4.687 eV

27. PHOTO-ELECTRIC EFFECT
calculations
For Copper:
Calculation of Cut-off Frequency
=
=
f
=
4.687 x 16 x 10
o =
o
Wo
h
-19
6.66 x 10
-34
J-sec.
J
7.4992 x 10
-19
6.66 x 10
-34
= 1.126 x 10 Hz
15
f 1.126 x 10 Hz
15

28. Thanks for Watching
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