State two factors that affect radiant flux intensity from a star.

Use the data given in Figure to show the validity of Wien's displacement law for $5000 \mathrm{K}$ and $4000 \mathrm{K}$.

The intensity- wavelength graph depends on the temperature of the object. For an object at a thermodynamic temperature $T$, the intensity against wavelength curve peaks at a wavelength ${\lambda }_{max}$.

Use Wien's displacement law to complete the table. Write your answers to two significant figures.

The luminosity of the star Aldebaran is 520 times that of the Sun. The wavelength of light at peak intensity for Aldebaran is $740 \mathrm{nm}$ and the wavelength of light at peak intensity for the Sun is $500 \mathrm{nm}$. Explain whether Aldebaran is cooler or hotter than the Sun. Radius of Aldebaran / radius of the Sun.

The luminosity of the star Aldebaran is 520 times that of the Sun. The wavelength of light at peak intensity for Aldebaran is $740 \mathrm{nm}$ and the wavelength of light at peak intensity for the Sun is $500 \mathrm{nm}$.

(b) Calculate the ratio:

Radius of Aldebaran / radius of the Sun.

The fractional change in the wavelength of the observed light from a galaxy is 0.15; its redshift is 15%.

Calculate its recession speed. State any assumptions made.

The Tadpole galaxy has a recession speed of $9400 \mathrm{km} {\mathrm{s}}^{-1}$.

Calculate the fractional change in the wavelength of the observed spectrum.