Intro to Electromagnetic waves Flashcards
State whether gamma carry more energy than radio waves, and why?
Yes, as they have a much higher frequency, and smaller wavelength.
What does Gauss’s law explain?
Explains the total electric flux through a closed surface is determined by the electric charge
What does Gauss’s Law for Magnetism do?
Total magnetic flux through any closed surface is equal to zero.
What does Faraday’s law explain?
How changing magnetic fields induce electric fields
What does Ampere Maxwell Law state?
Explains how changing electric fields induce magnetic fields
What is the framework for a compare and contrast question?
‘Similarly, light and EM____. Additionally, ___. Yet/Conversely …”
What was Maxwell able to do?
He was able to unify electricity and magnetism which were previously viewed as separate phenomena.
What did Maxwell also predict?
Electromagnetic waves would exist as transverse and self-propagating
What is the production of EM waves from?
Result from accelerating charges. An accelerating charge will create a changing electric field. Maxwell’s fourth equation predicts that it will induce a changing magnetic field.
Do EM waves require a medium?
No do not require a medium, in contrast to mechanical waves.
What is the biggest misconception in this topic?
That Maxwell ‘discovered or measured’ but he actually predicted mathematically
Who was the individual who proved Maxwell’s theory right?
Heinrich Hertz was the individual who gave the first experimental evidence to support Maxwell’s prediction of EM waves.
Explain his experiment
He utilised high voltage AC generated by an induction coil to create rapid sparling across the gap in the circuit, which indicated the transmission of electromagnetic waves.
What did Hertz show?
He showed that EM waves were polarised by showing how the spark generated would disappear when the loop was rotated 90 degrees. (parallel to the magnetic field)
Explain how induction coil is able to generate the radio waves.
type up my notes here
What is the value for the velocity of light?
3 x 10^8 m/s
What are the main historical investigations to remember?
- Galileo Galilei - lantern experiment
- Ole Romer - Measuring the relative velocity of Jupiter and the Earth - by timing the ellipses
- James Bradley - position of the sky change their position
- Hippolyte Fizeau - Used the cog wheel to increase the speed of rot. and measure the speed at which the light was reflected back
- Leon Foucalt
- Albert Michelson - eight sided mirror
What is the cavity resonator?
Creates a standing wave inside at specific frequencies
What is an interferometer?
Light from the same course of a known frequency is divided into two beams which travel equal paths and join back together to interfere constructively at a detector. The detector is then moved such that the light beams travel different distances and thus arrive out of phase.
