The origin of the Universe (a) Red giant and red shift are terms used in astronomy - Edexcel - GCSE Physics - Question 5 - 2017 - Paper 1

Red shift refers to the phenomenon where light from an object moving away from an observer is shifted to longer wavelengths, appearing redder than it would at rest. This effect is typically observed in distant galaxies, and it provides evidence for the expansion of the universe. The degree of red shift can be used to estimate the velocity at which a galaxy is receding from Earth.

First, calculate the change in wavelength:

$\text{change in wavelength} = 478 ext{ nm} - 434 ext{ nm} = 44 ext{ nm}$

Next, find the recessional speed using the formula:

$\text{recessional speed} = \frac{\text{change in wavelength}}{\text{original wavelength}} \times \text{speed of light}$

Substituting values in:

$\text{recessional speed} = \frac{44 ext{ nm}}{434 ext{ nm}} \times 3.00 \times 10^8 ext{ m/s}$

Calculating gives:

$\text{recessional speed} = 0.1014 \times 3.00 \times 10^8 ext{ m/s} = 3.042 \times 10^7 ext{ m/s}$

Thus, the recessional speed of the galaxy is approximately 30,420,000 m/s.