IB Physics SL C 5 3 Light Doppler Approximation Questions

Apply the low-speed light Doppler approximation to red-shift, blue-shift, radar speed, spectral lines and Hubble-law calculations.

Exam points

apply the low-speed light Doppler approximation to relate fractional frequency or wavelength shift to source speed and the speed of light
calculate recession or approach speed from shifted spectral lines, red-shift factor, radar frequency change and reflected-signal evidence
use red-shift and Hubble law to calculate galaxy distance or the Hubble constant and interpret the factor of two in radar reflection

Learn this topic

Study C.5.3—Light Doppler approximation conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 2]

Star A is a main sequence star.

The data for Star A and the Sun are given in a table.

Table for Question IB Physics SL C 5 3 Light Doppler Approximation Questions question 1 — IB Physics SL

Determine the speed, in $\mathrm{km} \mathrm{s}^{-1}$ , of Star A relative to Earth.

$\begin{aligned} v=\frac{\Delta \lambda}{\lambda} c=\frac{0.007}{100} \times 3 \times 10^{8}=21000 21 \mathrm{~km} \mathrm{~s}^{-1} \end{aligned}$

Allow ECF for MP2.

Do not award MP1 for use of the Doppler formulas for sound and mechanical waves.

[2]

All question bank results loaded

Learn this topic

IB Physics SL C 5 3 Light Doppler Approximation Questions question 1