Which statement is correct about radiant flux intensity?

(A) It depends on the area of the measuring device.

(B) It is measured in ${\mathrm{Wm}}^{-2}$.

(C) It is the same as luminosity.

(D) It is the total radiant power emitted from a star.

A group of astronomers have determined the radiant flux intensity F from a star and its distance d. The percentage uncertainty in F is $1.2\%$ and the percentage uncertainty in d is $2.5\%$. What is the percentage uncertainty in the calculated value of the luminosity of the star?

A particular emission spectral line is measured in the laboratory to have a frequency of $7.3\times {10}^{14} \mathrm{Hz}$. Calculate the wavelength of this spectral line in the laboratory.

A particular emission spectral line is measured in the laboratory to have a frequency of $7.3\times {10}^{14} \mathrm{Hz}$.

(b) Calculate the observed wavelength of this same spectral line in the spectrum of a galaxy moving away from the Earth at a speed of:

(i) $11{\mathrm{Mms}}^{-1}$

A particular emission spectral line is measured in the laboratory to have a frequency of $7.3\times {10}^{14} \mathrm{Hz}$. Calculate the observed wavelength of this same spectral line in the spectrum of a galaxy moving away from the Earth at a speed of $7.0\%$ the speed of light.

A particular emission spectral line is measured in the laboratory to have a frequency of $7.3\times {10}^{14} \mathrm{Hz}$. The spectrum of all distant galaxies is redshifted. State and explain what you can deduce about the Universe.

The recession speed $v$ against distance $d$ graph for some galaxies is shown.

Determine the Hubble constant from this graph. Explain your answer.

The Big Bang occurred some 14 billion years ago.

$1 \text{years} \approx 3.15\times {10}^{-7}\mathrm{s}$

Estimate the farthest distance we can observe. Explain your answer.