DP Physics (last assessment 2024)

Test builder »

Question 23M.3.HL.TZ2.18

Select a Test
Date May 2023 Marks available [Maximum mark: 6] Reference code 23M.3.HL.TZ2.18
Level HL Paper 3 Time zone TZ2
Command term Calculate, Determine, State Question number 18 Adapted from N/A
18.
[Maximum mark: 6]
23M.3.HL.TZ2.18

Galaxy D has a redshift z = 0.13.

(a)

Calculate, in Mpc, the distance to D using a Hubble constant value of 73 km s−1 Mpc−1.

[2]

Markscheme

ALTERNATIVE 1

v = 0.13 × 3 × 108 OR 0.39 × 108 «m s−1» OR 0.13 × 3 × 105 OR 0.39 × 105 «km s−1» ✓

d = «0.39×10873×103 =» 530 «Mpc» ✓

 

ALTERNATIVE 2

d = czH

«3 × 108 × 0.1373×103 =» 530 «Mpc» ✓

 

Award [2] for BCA

(b)

A Hubble constant value of 73 km s−1 Mpc−1 gives an age of the universe to be 13.4 × 109 years when assuming a constant rate of expansion has occurred.

(b.i)

Determine in years, the age of the universe when the light detected on Earth now was originally emitted from D.

[3]

Markscheme

ALTERNATIVE 1

RR0 = 1 + z = 1.13 ✓

RR0 = tt0 = 1.13 ✓

t0 = «13.4×1091.13 =» 11.9 × 109 «years» ✓

 

MP1 can be awarded if MP2 is clearly seen

For MP2 allow Hnow / Hthen = 1.13 then Hthen= 1/t0

Award [3] for BCA

Allow ECF for MP3

 

ALTERNATIVE 2

«distance light travelled from galaxy = » 530 × 106 × 3.26 OR 1.7 × 109 «ly» ✓

light emitted from galaxy 1.7 × 109 «years ago» ✓

age when light was emitted «13.4 × 109 − 1.7 × 109 =» 11.7 × 109 «years ago» ✓

 

Accept 1.6 × 1025 m for MP1

(b.ii)

Evidence based on observations of type I a supernovae affects the result in (b)(i).
State the relevant conclusion from these observations.

[1]

Markscheme

evidence from type Ia supernovae show an accelerating universe ✓

 

Accept distant galaxies are further away than expected