Cosmology HW answers

 

1      C

2      A

M3.(a)      (i)      Spectral line moved to longer wavelength position (allow ‘to red end of spectrum’)

B1

(ii)     Mention of Doppler effect

B1

Expansion of universe / Big Bang

B1

Wavelength increased (or frequency decreased)

B1

Successive ‘peaks’ of wave emitted at increasing distance
from Earth [allow ‘wave stretched’]

B1

Wavelength observed on Earth increases compared with
source stationary

B1

max 4

the use of physics terms is accurate, the answer is fluent / well argued with few errors in spelling, punctuation and grammar

B2

award for 2+
the use of physics terms is accurate, but the answer lacks coherence or the spelling, punctuation and grammar are poor

B1

award for 1
the use of physics terms is inaccurate, and the answer is disjointed with significant errors in spelling, punctuation max 2 and grammar

B0

max 2

(b)     (i)      use of c = fλ
Δf = 3 × 10⁸ /(561 × 10^–9) – 3 × 10⁸ / (540 × 10^–9)

C1

= (5.348 – 5.556) × 10¹⁴ [= 2.08 × 10¹³ Hz]

M1

[explicit subtraction or to 3+ s.f. required for A mark]

A1

(ii)     Δf / f = v / c

V = c * Δf / f [or Δλ / λ] = 3 × 10⁸ × 2.08 × 10¹³ / 5.556 × 10¹⁴

C1

[ecf from bi]

M1

= 1.12 × 10⁷ m / s

A1

(iii)     [d = v / H]
conversion to km / s

C1

d = 11.2 × 10³ / 65 = [172 Mpc] [ecf from bii]

B1

= 172 × 10⁶ × 3 × 10¹⁶ = 5.17 × 10²⁴ m

A1

[16]

 

M4.(a)

 

P moving away, Q towards (1)

λ increasing and decreasing respectively (1)

(4)

(b)     (i)      

 (1)

(max 8)

[12]