Question 19M.3.SL.TZ2.14
| Date | May 2019 | Marks available | [Maximum mark: 6] | Reference code | 19M.3.SL.TZ2.14 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Calculate, Outline, Show that | Question number | 14 | Adapted from | N/A |
The Hubble constant is 2.3 × 10-18 s-1.
A galaxy is 1.6 × 108 ly from Earth. Show that its recessional speed as measured from Earth is about 3.5 × 106 m s-1.
[2]
d = «1.6 × 108 × 9.46 × 1015 =» 1.51 × 1024 «m»✔
v = «H0d = 2.3 × 10−18 ×1.5 × 1024 =» 3.48 × 106 «m s–1» ✔
Answer given, correct working required or at least 3sf needed for MP2.
This very simple application of Hubble’s law was answered correctly by the vast majority of candidates.
A line in the hydrogen spectrum when measured on Earth has a wavelength of 486 nm. Calculate, in nm, the wavelength of the same hydrogen line when observed in the galaxy’s emission spectrum.
[2]
» 5.64«nm» ✔
observed λ = «486 + 5.64 =» 492 «nm»✔
Many candidates subtracted the change in wavelength and obtained a blue shift. Others were unsure which wavelength λo is in the data book equation. But correct answers were common.
The Hubble constant is 2.3 × 10-18 s-1.
Outline how observations of spectra from distant galaxies provide evidence that the universe is expanding.
[1]
all distant galaxies exhibit red-shift ✔
OWTTE
Outline how observations of spectra from distant galaxies provide evidence that the universe is expanding.
[1]
all distant galaxies exhibit red-shift ✔
OWTTE
Nearly all candidates were able to mention redshift as the evidence for galaxy recession and the universe expansion.