1- Chapter 12 - Special Relativity

Question 1

The Lorentz factor = (γ)

Answer 1

Question 2

non relativlistic 1 way doppler shift.

Answer 2

1+ v/c for v<<<c>
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Question 3

relatgivlistic 1 way dopler shift

Answer 3

γ(1+v/c) or ( (1+v/c)/(1-v/c) )^1/2

Question 4

2 way relativlistic doppler shift

Answer 4

(1+v/c) / (1-v/c)

Question 5

time dilation.

Answer 5

t=γτ(tau)

τ-frame of event

t-frame from observed

Question 6

v/c = (in t₁ and t₂)

Answer 6

(t₂-t₁)/(t₂+t₁)

Question 7

t₂/t₁=

Answer 7

(1+v/c) / (1-v/c)

Question 8

λ_r/λ_e=

Answer 8

1+v/c

Question 9

v/c= (in λ)

Answer 9

Δλ/λ for v<<

Question 10

what is t₁ (or Δtout)

Answer 10

the time interval between sending 2 pulses

Question 11

what is t₂ (or Δt_back)

Answer 11

the time between reciving the 2 reflected pulses

Question 12

What is a parsec

Answer 12

The distance to a star when the parralax angle it subtends is 1 second of an arc.

1^o=60mins=3600 seconds of an arc.

Question 13

What is radar ranging?

Answer 13

a way of measuring distance by sending a pulse to an object and measure the time taken.

(assuming its travellling at constant speed c)

Question 14

Δλ/λ = (1 way and 2 way)

Answer 14

1. v/c
2. 2v/c

Question 15

Hubbles law?

Answer 15

Plot speed of recession vs distance of a galaxy from earth.

v=H₀r

Where H₀ is the hubble constant and the reciprical of the age of the universe.

Question 16

How brightness can be used to calculate distance

Answer 16

Assuming the brigneset star in one cluster is the same as another cluster you can work out the intensite difference , then use inverse sqaure law to find distance.

Question 17

What is cosmalogical redshift?

Answer 17

λ_observed/λ_emmited = R_observed/R_emmited​ = 1 + Δλ/λ = 1+Z

R is distance

Caused by the expansion of the universe, which stretches the wavelengths of observeed light depending on the distance its travelled.

Question 18

HOw can mass of a a thing be found?

Answer 18

the velocity of something orbiting it, and the orbit radius.

Question 19

What did the universe used to be like

Answer 19

much smaller and hotter.

Question 20

what is cosmic background raditation?

Answer 20

The largest red shifted light. IT was produced when the univesrse became cool enough for neutral atoms to form first relased as 1x10^-6 m wavelength now 1x10^-3m.

The temperature of the universe if also proportinal to this change in wavelength.