In this unit, you created one concept map and analyzed and/or created another. Both maps focus on the major revolutions in modern physics: the Special Theory of Relativity (and the thought experiments involved) and the discovery of, and further exploration prompted by, the photoelectric effect. Pretend that you are writing for someone who has not yet studied grade 12 physics and explain to the student the development of the theories based on thought and experimental evidence. Also discuss the impact of these two major revolutions. Some things to consider—the major stepping stones to the development of the theories, the main people involved, what this means to the world in terms of technology, etc... Keep your response to within 200 words.
An informative essay should present about 10 details (related to the following list ) explained such that it is clear the student understands the material and that a person who has not studied grade 12 physics can understand the concepts.
Michelson- Morley experiment and the constancy of the speed of light
Einstein’s Theory of Special Relativity
Time Dilation (even time is relative when objects are travelling at relativistic speeds)
At least one piece of evidence that Time Dilation occurs
Length contraction (must be happening if time dilation is happening)
Conservation of Mass-Energy , and proof that it occurs
Blackbody Radiation and Planck’s hypothesis
The Photoelectric effect
Einstein’s Quantum Theory (perhaps even a sketch of the graph)
The Compton effect (conservation of momentum and energy during photon interactions)
Pair production
de Broglie’s wavelengths and electron diffraction
Applications of quantum physics (related back to application assignment – e.g., medical, nuclear power, atomic bomb)
In the late 1800s, scientists believed that the speed of light was determined by the medium through which it travelled. However, the Michelson-Morley experiment showed that the speed of light is constant, regardless of the medium. This experiment paved the way for Einstein’s Theory of Special Relativity, where he proposed that time and space are relative and depend on the observer’s motion. This theory was based on thought experiments, such as the famous “twin paradox,” and was later confirmed by experiments such as the Hafele-Keating experiment. One consequence of special relativity is time dilation, which means that time appears to slow down for objects that are moving at relativistic speeds. Evidence for this phenomenon comes from particle accelerators, where high-speed particles have longer lifetimes than they would if they were at rest. Special relativity also predicts length contraction, which means that objects appear shorter when moving at relativistic speeds.
Another major revolution in modern physics was the discovery of the photoelectric effect. This phenomenon occurs when photons of light eject electrons from a metal surface. Planck’s hypothesis, that energy is quantized, explained this phenomenon and led to the development of Einstein’s Quantum Theory. This theory proposed that light behaves as both a particle and a wave, and that the energy of a photon is proportional to its frequency. This theory was confirmed by experiments like the Compton effect and pair production. Moreover, de Broglie’s wavelengths and electron diffraction also showed that matter behaves as both a particle and a wave.
The impact of these two major revolutions in modern physics cannot be overstated. Special relativity led to the development of technologies like GPS (which depends on measurements of time) and nuclear power. Quantum mechanics underpins the technologies behind electronics, computers, and information technology, while also having applications in medicine, such as in magnetic resonance imaging (MRI). However, it’s worth acknowledging that these discoveries also had less desirable outcomes, like the development of the atomic bomb. Overall, the theories of special relativity and quantum mechanics have revolutionized our understanding of the universe and opened up new frontiers of scientific inquiry.