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NSWPhysicsQuick questions
Module 7: The Nature of Light
Quick questions on The electromagnetic spectrum and Maxwell's equations: HSC Physics Module 7
9short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the spectrum?Show answer
Electromagnetic (EM) radiation is a transverse wave of oscillating electric and magnetic fields propagating at the speed of light, $c = 2.998 \times 10^8$ m/s in vacuum. The fields are perpendicular to each other and to the direction of propagation. EM waves do not need a medium.
What is key relationships?Show answer
For a wave of frequency $f$ and wavelength $\lambda$ travelling at speed $c$:
What is maxwell's equations, in words?Show answer
By 1865, James Clerk Maxwell had combined four laws of electromagnetism into a self-consistent set:
What is what an EM wave looks like?Show answer
At a snapshot in time, a plane EM wave travelling in the $+x$ direction has:
What is worked example?Show answer
A green photon ($\lambda = 550$ nm) and a UV photon ($\lambda = 200$ nm):
What is confusing wavelength and frequency order?Show answer
As wavelength increases, frequency decreases, and photon energy decreases.
What is stating that EM waves need a medium?Show answer
They do not; this is the difference from sound waves.
What is quoting $c$ as the speed of light in glass?Show answer
$c$ is the speed in vacuum. In glass, light slows by the refractive index, but the frequency stays the same.
What is confusing $\mu_0$ and $\varepsilon_0$?Show answer
$\mu_0$ is the magnetic constant, $\varepsilon_0$ is the electric (permittivity) constant. Both are measured in entirely electrostatic and magnetostatic experiments.