PhotoElectric Effect 1

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1. A photon of light has a frequency 5 x 1016Hz.
Answer the following questions.

1.1. What is meant by the term "frequency"?
number of cycles per second
Audio 1.1

1.2. Are light waves longitudinal or transverse? Name the experiment that proves this.
Transverse
Polarisation
Audio 1.2

1.3. Calculate the energy of this photon.
E = hf
E = (6,63 x 10-34)(5 x 1016)
E = 3,315 x 10-17J
Audio 1.3

1.4. Calculate the wavelength of this photon.
c = fλ
3 x 108 = 5 x 1016λ
λ = 6 x 10-9m
Audio 1.4

1.5 Calculate the period.

Audio 1.5

2. A photon of light has wavelength of 4 x 10-8m.
Answer the following.

2.1 Calculate the frequency.
v = fλ
3 x 108 = f(4 x 10-8)
f = 7,5 x 1015Hz
Audio 2.1

2.2 Calculate the energy of the photon
E = hf
E = (6,63 x 10-34)(7,5 x 1015)
E = 4,97 x 10-18J
Audio 2.2

3. What is meant by "the photoelectric effect"?
The emmision of electrons from the surface of a substance by the action of light.
Audio 3

4. What is meant by the term "work function?"
This is the minimum amount of energy needed to free an electron from that substance.
Audio 4

5. What does the photoelectric effect tell us about the nature of light?
Light has a particle nature.
Audio 5

6. What is meant by "threshold frequency"?
This is the lowest frequency of light that can cause ejection of electrons from a substance.
Audio 6

7. What is meant by "quanta"?
• packages of energy (energy unit)
• radiated energy is quantized
• it exists in multiples of a smallest possible value
Audio 7

8. What are "photons"?
• quanta of electromagnetic radiation
• the incoming (incident) light
Audio 8

9. What are "photoelectrons"?
These are simply the electrons that are ejected from the metal by the action of light (photons).
Audio 9

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