Electromagnetic Radiation
• Outline
– The nature of electromagnetic radiation.
– Light as energy.
– The workfunction of metals.
docsity.com
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Guidelines and tips
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Understanding Electromagnetic Radiation: Wave-Particle Duality, Slides of Chemical Principles
An in-depth exploration of electromagnetic radiation, discussing its nature as a form of energy with both electric and magnetic components. It covers the concepts of wavelength, frequency, and the relationship between them, as well as the photoelectric effect and the wave-particle duality of light. Students will gain a solid understanding of the properties and behavior of electromagnetic radiation.
Typology: Slides
2013/2014
1 / 22
This page cannot be seen from the preview
Don't miss anything!
Related documents
Partial preview of the text
Download Understanding Electromagnetic Radiation: Wave-Particle Duality and more Slides Chemical Principles in PDF only on Docsity!
Electromagnetic Radiation
• Outline
- The nature of electromagnetic radiation.– Light as energy.– The workfunction of metals.
Electromagnetic Radiation
• Electromagnetic radiation or “light” is a
form of energy.
• Characterized by:
–Wavelength (
–Amplitude (A)
• Has both electric (E) and magnetic (H)
components.
Electromagnetic Radiation (cont.)•
Wavelength (
): The distance between two
consecutive peaks in the wave.
Increasing Wavelength
1
2
3
Unit: length (m)
Electromagnetic Radiation (cont.)•
Frequency (
): The number of waves (or cycles)
that pass a given point in space per second.
Decreasing Frequency
1
2
3
Units: 1/time (1/sec)
Electromagnetic Radiation (cont.)•
We classify electromagnetic radiation bywavelength.
Visible radiation takes up only a small part of theelectromagnetic spectrum.
What statement is true when comparing red lightto blue light?
A. Red light travels at a greater speed than blue light.B. Blue light travels at greater speed than red light.C. The wavelength of blue light is longer.D. The wavelength of red light is longer.
Light as Energy (cont.)
• Planck’s experiments on light emitted from
a solid heated to “incandescence”.
As body is heated, intensity
increases, and peak wavelengthshifts to smaller wavelengths.Can “classical” physicsreproduce this observation?
Light as Energy (cont.)
Comparison of experiment to the “classical”prediction:
Classical prediction isfor significantly higherintensity as smallerwavelengths than whatis observed.
“The Ultraviolet Catastrophe”
Light as Energy (cont.)
In general the relationship between frequency and“photon” energy is
E
photon
= h
- Example: What is the energy of a 500 nm photon?
= c/
= (3x
8
m/s)/(5.0 x 10
m)
= 6 x 10
14
1/s
E = h
=(6.626 x 10
J.s)(6 x 10
14
1/s) = 4 x 10
J
Which type of photon will have the largest energy?
A. UltravioletB. X-Ray
C. MicrowaveD. Visible
The Photoelectric Effect
- Shine light on a metal and observe
electrons that are released.
- Find that one needs a minimum
amount of photon energy to seeelectrons (“
o
- Also find that for
o
number of electrons increases linearly with light intensity.
metal
The Photoelectric Effect (cont.)
The Photoelectric Effect (cont.)
- For Na with
= 4.4 x 10
J,
what wavelength corresponds to
o
m
e
2
h
photon
h
= 4.4 x 10
J
hc
= 4.4 x 10
J
hc
x
10
19
J
x
10
34
J
.
s
3
x
10
(^8)
m
/
s
x
10
19
J
= 4.52 x 10
m = 452 nm
0
0 Frequency (
)
docsity.com
In a workfunction experiment using 300 nm light, theelectrons ejected from Potassium (K) have a greatervelocity that those ejected from Sodium (Na).Therefore:
A.
Na
K
B.
K
Na
C.
K
Na
D.
K
metal