Physics grade 12.pdf explore the concept

Photoelectric effect

1. PHYSICSGRADE 12
LESSON
Optical Phenomenon : Photoelectric effect
Complied by M Ndhlovu

2. WHAT IS LIGHT
•Light is a form ofelectromagnetic radiationthat is visible to the
human eye, occupying a small portion of theelectromagnetic
spectrum. It consists of oscillatingelectric and magnetic
fieldsthat propagate as waves through space at the speed of light
(~3 × 10⁸ m/s in a vacuum)
2
Light, in its particle manifestation, consists ofdiscrete energy quanta
(photons) that are excitations of an underlying solitary
wave field. These photons are not independent mass-
bearing particles but rather localized disturbances propagating
at the speed of light,
governed by the wave medium that fills the universe.

3. SPEAKING IMPACT
Your ability to communicate effectively
will leave a lasting impact on your
audience
Effectively communicating involves not
only delivering a message but also
resonating with the experiences, values,
and emotions of those listening
3

4. THE
PHOTO-ELECTRIC EFFECT
4

5. PHOTOELECTRIC EFFECT…
•Thephotoelectric effectoccurs when a material (often a metal)
releases electrons after being exposed to electromagnetic radiation,
such as visible or ultraviolet light. This phenomenon demonstrates
that light exhibitsparticle-like behavior, as it transfers energy in
concentrated bundles calledphotonsrather than as a continuous
wave. The discovery of this effect was crucial in
establishingquantum theory, proving that energy is not continuous
but instead comes in fixed, quantized amounts
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6. THRESHOLD VS WORK FUNCTION
Threshold frequency:
It is the minimum frequency of light
required to eject electrons from a
material.
If the frequency of light is less than
the threshold frequency, the electrons
will not be emitted from the material.
Work function:
It is the minimum energy required to
remove an electron from a material.
It is defined as the energy difference
between the energy of an electron at
the surface of a material and the energy
of an electron at an infinite distance
from the material
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φ = hf
Where h is Planck’s constant
f is the frequency of radiation
work function (φ)

7. ENERGY OF A PHOTON
•E =hν
•Where:
•E= Energy of the photon (injoules, J)
•h=Planck’s constant(6.626×10−34J⋅s6.626×10−34J⋅s)
•ν = Frequency of the light wave (inhertz, Hz)
Since frequency (ν) and wavelength (λ) are
related byc=λν
(wherec= speed of light), the photon energy
can also be expressed as:
E=hc/λ
Where:
λ= Wavelength of light (inmeters, m)
c= Speed of light (3×108m/s3×108m/s)
7
Theenergy of a photonis the discrete (quantized) amount of electromagnetic energy
carried by a single photon, which is the smallest possible packet (quantum) of light or other electromagnetic
radiation.

8. PHOTOEMISSION
•Occurs when electrons get
ejected from a metal surface
•Conditions for Photoemission
hν>Φ
hν=Φ
hν<Φ
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Electronsejected(withKE>0)
Thresholdejection(KE=0)
Noejection(evenwithhighintensity)

9. APPLICATION OF THE PHOTOELECTRIC EFFECT IN
SA
9
Technology
Lasers, Telescopes and Photography
Medicine
MRI, CT scans and Laser surgery

10. EP H O T O N=Φ+KEMAX
MATHEMATICAL
REPRESATATION
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11. THANK YOU
Yengbatican (2020) Electromagneticwaves from Slideshare at electromagneticwaves-
150729203749-lva1-app6891.pptx (Accessed 17 August 2025)
Pascua, D. Reyes, M (2016) Photoelectric effect from Slideshare at Grade 12 433042179-
photoelectric-pptx.pptx (Accessed 17 August 2025)
Mabokodo, M (2019) Photoelectric effect Absoption and Emission spectra from slideshare at
Photoelectric Effect and Absorption and Emission Spectra Presentation | PPT (Accessed 17 Augst 2025))
Sanchez, M (2021) Application of the Photoelectric Effect at Slideshare
THE NATURE OF LIGHT:EXPLORE THE PHYSICSs | PPTX (Accessed 17 August 2025)
Webmistress (2025) The graph, Photoelectric Effect.
Available at: https://www.cyberphysics.co.uk/topics/atomic/Photoelectric_effect/Photoelectric_effect_graph.htm
(Accessed: 18 August 2025).

12. Yengbatican (2020) Electromagneticwaves imgurl:https://image.slidesharecdn.com/electromagneticwaves-
150729203749-lva1-app6891-25081804481
7-0f9b5197/75/electromagneticwaves-
150729203749-lva1-app6891-pptx-6-2048.jpg - Search
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