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Unit 2 Electricity and Light

8 dot points across 8 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

What is electric current at the level of moving charge carriers?

Current as the rate of flow of charge, the equation I = nAve linking current to charge-carrier density and drift velocity, and conductors, semiconductors and insulators.
A focused answer to WJEC A-Level Physics Unit 2 conduction of electricity, covering current as the rate of flow of charge, the equation I = nAve linking current to charge-carrier number density and drift velocity, and the difference between conductors, semiconductors and insulators.
11 min answer →

How do Kirchhoff's laws, internal resistance and potential dividers let us analyse a DC circuit?

Kirchhoff's first and second laws, series and parallel resistors, EMF and internal resistance, and the potential divider.
A focused answer to WJEC A-Level Physics Unit 2 DC circuits, covering Kirchhoff's first and second laws, combining resistors in series and parallel, EMF and internal resistance, and the potential divider.
11 min answer →

How does stimulated emission and a population inversion produce coherent laser light?

Energy levels and photon emission, spontaneous and stimulated emission, population inversion and pumping, and the properties of laser light.
A focused answer to WJEC A-Level Physics Unit 2 lasers, covering atomic energy levels and photon emission, spontaneous and stimulated emission, population inversion and pumping, the optical cavity, and the properties of laser light.
11 min answer →

What does the photoelectric effect tell us about the nature of light?

The photon model and E = hf, the photoelectric effect, Einstein's photoelectric equation, the work function and threshold frequency.
A focused answer to WJEC A-Level Physics Unit 2 photons, covering the photon model and E = hf, the photoelectric effect, Einstein's photoelectric equation, the work function and threshold frequency, and why the wave model fails.
11 min answer →

Why does light bend at a boundary, and when is it totally internally reflected?

Refraction and refractive index, Snell's law, the critical angle, total internal reflection, and optical fibres.
A focused answer to WJEC A-Level Physics Unit 2 refraction of light, covering refraction and refractive index, Snell's law, the critical angle, total internal reflection, and how optical fibres guide light.
11 min answer →

What is resistance, when does Ohm's law hold, and how does resistivity depend on the material?

Resistance, Ohm's law, I-V characteristics of a metal, filament lamp and diode, resistivity, and the effect of temperature.
A focused answer to WJEC A-Level Physics Unit 2 resistance, covering the definition of resistance, Ohm's law, the I-V characteristics of a metallic conductor, filament lamp and diode, resistivity, and how temperature affects resistance.
11 min answer →

What is a wave, and how do transverse and longitudinal waves differ?

Transverse and longitudinal waves, amplitude, wavelength, frequency, period and phase, the wave equation, and polarisation.
A focused answer to WJEC A-Level Physics Unit 2 the nature of waves, covering transverse and longitudinal waves, amplitude, wavelength, frequency, period and phase, the wave equation, and polarisation as evidence of transverse waves.
11 min answer →

How do superposition, interference and diffraction let us measure wavelength?

Superposition and coherence, two-source interference and path difference, diffraction, and the diffraction grating equation.
A focused answer to WJEC A-Level Physics Unit 2 wave properties, covering superposition and coherence, two-source interference and path difference, diffraction, and using the diffraction grating equation to measure the wavelength of light.
11 min answer →