CCEA A-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Internal Resistance and Potential Dividers
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Deformation of Solids
Thermal Physics
Uniform Circular Motion
Simple Harmonic Motion
The Nucleus and Radioactive Decay
Nuclear Energy, Fission and Fusion
Gravitational Fields
Electric Fields
Capacitors
Magnetic Fields
Charged Particles and Accelerators
Astronomy
Hubble's law
- 3 things to know
- Unit AS 2
Overview
Hubble's law, defining each symbol with its unit and value of the Hubble constant with its unit.
What you need to know
Answer each one before you reveal it.
Why must the distance to a galaxy be found by a method independent of its red shift?
State Hubble's law, defining each symbol with its unit.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State Hubble's law, defining each symbol with its unit.
Model answer
v = H₀d, where v is the speed of recession of a galaxy in m s⁻¹, H₀ is the Hubble constant in s⁻¹ and d is the distance to the galaxy in metres.
- 2
State the value of the Hubble constant with its unit.
Model answer
The Hubble constant is approximately 2.4 × 10⁻¹⁸ s⁻¹.
- 3
Why is the unit of the Hubble constant s⁻¹?
Model answer
Because it is a speed divided by a distance, and m s⁻¹ divided by m leaves s⁻¹.
- 4
What is the shape of a graph of recession speed against distance for distant galaxies, and what does its gradient give?
Model answer
It is a straight line through the origin, and its gradient is the Hubble constant.
- 5
A galaxy recedes at 3.70 × 10⁶ m s⁻¹. Calculate its distance, taking the Hubble constant as 2.4 × 10⁻¹⁸ s⁻¹.
Model answer
d = v/H₀ = 3.70 × 10⁶ / 2.4 × 10⁻¹⁸ = 1.5 × 10²⁴ m, and 2.4 × 10⁻¹⁸ × 1.54 × 10²⁴ returns 3.70 × 10⁶ m s⁻¹ as given.
- 6
A galaxy recedes at 6.40 × 10⁶ m s⁻¹. Calculate its distance, taking the Hubble constant as 2.4 × 10⁻¹⁸ s⁻¹.
Model answer
d = v/H₀ = 6.40 × 10⁶ / 2.4 × 10⁻¹⁸ = 2.7 × 10²⁴ m, and 2.4 × 10⁻¹⁸ × 2.67 × 10²⁴ returns 6.40 × 10⁶ m s⁻¹.
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