A-Level Physics OCR A H556

5.5.2: Electromagnetic radiation from stars

#5.5.2a

energy levels of electrons in isolated gas atoms

#5.5.2b

the idea that energy levels have negative values

#5.5.2c

emission spectral lines from hot gases in terms of emission of photons and transition of electrons between discrete energy levels

#5.5.2d

the equations $hf = ΔE$ and $\dfrac{hc}{λ} = ΔE$

Learners will also require knowledge of section 4.5

#5.5.2e

different atoms have different spectral lines which can be used to identify elements within stars

#5.5.2f

continuous spectrum, emission line spectrum and absorption line spectrum

#5.5.2g

transmission diffraction grating used to determine the wavelength of light

The structure and use of an optical spectrometer are not required; PAG 5

#5.5.2h

the condition for maxima $d\sin{θ} = nλ$ , where d is the grating spacing

Proof of this equation is not required.

#5.5.2i

use of Wien’s displacement law $λ_{max} ∝ \dfrac{1}{T}$ to estimate the peak surface temperature (of a star)

#5.5.2j

luminosity L of a star; Stefan’s law $L = 4πr^2σT^4$ where σ is the Stefan constant

Learners will also require knowledge of 4.4.1

#5.5.2k

use of Wien’s displacement law and Stefan’s law to estimate the radius of a star.

5.5.1

Stars

5.5.3

Cosmology