Day - 16

Homework Chapter 3: Due Wednesday Feb. 24
Smartworks Chapters 4 & 5 are also posted
Exam 2 will cover chapters 3, 4, & 5
Ranking Task (Gravity) due now.
1 st quarter observing night:
Wednesday!!

• Hydrogen atom simulator
• Splash page warm up

• Newton, Remember Newton? He did more than just calculus and mechanics.
• In the 17th Century, Isaac Newton argued that light was composed of little particles while Christian
Huygens suggested that light travels in the form of waves.
• In the 19 th and 20 th Century Maxwell, Young,
Einstein and others were able to show that Light behaves both like a particle and a wave depending on how you observe it.

Thomas Young’s interference experiment

Scottish physicist James Clerk Maxwell showed mathematically in the 1860s that light must be a combination of electric and magnetic fields.

In 1905 Einstein calculated the energy of a particle of light (
and proposed the photoelectric effect. photon
E photon
= hc/
 e-

Light comes from the acceleration of charged particles (such as electrons and protons)

But, where does light actually come from?
electron
Accelerating charges produce light – electromagnetic radiation!

The Electro-Magnetic (EM) Spectrum
• The EM spectrum covers the entire range of wavelengths.
• All waves travel at one speed (c, the speed of light).

Tutorial: – p.45
EM Spectrum of Light
• Read the instructions and questions carefully.
• Discuss the concepts and your answers with one another. Take time to understand it now!!!!
• Come to a consensus answer you both agree on.
• If you get stuck or are not sure of your answer, ask another group.
• Work with a partner!
• 5 minutes

An atom consists of a small, dense nucleus (containing protons and neutrons) surrounded by electrons
Model Proposed by Niels Bohr 1913

Atoms are mostly empty space
A nucleus is about 10 -15 m in size and the first electron orbits out at
10 -10 m from the center of the atom – The size of the electron orbit is
100,000 times greater than the size of the nucleus

So if a nucleus the size of an orange (10 cm) was located at the center of the football field, where would the electron be?
End Zone?
Grandstands?
On Campus?
In Clarksville?

If the electron’s orbit is
100,000 times bigger than the nucleus then the electron would be
10,000 m or 6.21 miles away from the center of the Football Field!
Still in Clarksville, but near exit 11.

The electron should be thought of as a distribution or cloud of probability around the nucleus that onaverage behave like a point particle on a fixed circular path

Nucleus

Photons (light-waves) are emitted from an atom when an electron moves from a higher energy level to a lower energy level
Nucleus

Photons (light-waves) can also be absorbed by an atom when an electron moves from a lower energy level to a higher energy level
Nucleus

• Hydrogen atom simulator

Tutorial: – p.63
Light & Atoms
• Read the instructions and questions carefully.
• Discuss the concepts and your answers with one another. Take time to understand it now!!!!
• Come to a consensus answer you both agree on.
• If you get stuck or are not sure of your answer, ask another group.
• Work with a partner!
• 15 minutes