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1	Use the data below to show that the power of the star V Tau (Zeta Tauri) is approximately 4 × 1030 W.
	Intensity =	1.9 × 10–8 W m–2
	Distance from Earth =	4.0 × 1018 m
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2.	(a)	(i)	The equation I = P/ 4pD2 can be used to determine the power output P of a star of known distance D and intensity I. 
Calculate the luminosity of a star which has a measured intensity of 1370 W m–2 and which is known to be 1.49 × 1011 m from Earth.
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3.	When the Sun was formed some 4.6 × 109 years ago, it was slightly smaller than it is today. Theoretical calculations show that it has become 40% more luminous and grown in radius by 6% (i.e. P = 1.4 P and r = 1.06 r where L and r represent the luminosity and radius of the Sun when it was formed).
Data for the Sun today:
Power Output  P	= 3.9 × 1026 W
Radius r	= 7.0 × 105 km
Temperature T	= 5800 K
(i)	Calculate the power output of the Sun when it was formed.
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(2)
(ii)	Calculate the surface area of the Sun when it was formed.
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(2)
(iii)	Hence show that the surface temperature of the Sun has increased by approximately 300 K during its lifetime.
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(4)

(iv)	The Sun has become slightly more yellow during its lifetime. It used to be more orange in colour. This is because the wavelength at which the peak intensity of its emitted radiation occurs has decreased. Use Wien’s law to calculate the decrease in the wavelength of the peak intensity.
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(3)
(b)	The graphs show the sensitivity of a particular brand of photographic film and that of a charge coupled device, CCD, to different parts of the electromagnetic spectrum.

	The surface temperature of a star can be calculated once the wavelength of the peak of its spectrum (lmax) is known. Use the graphs to explain why photographic film would be less suitable than CCDs for determining lmax of a star which radiates mainly in the visible region (400 nm – 700 nm) of the electromagnetic spectrum.
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(3)
	State one other advantage of using CCDs suggested by these graphs.

4.	The graph shows the relative intensity of the energy distribution in the spectrum of a body radiating at a temperature of 6000 K (the approximate temperature of the Sun).

	Use Wien’s law,  = 3.9 × 10–3 m K, to estimate the wavelength at which the intensity of radiation from the Earth is a maximum.
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(2)
	Add a second curve to the graph to show the approximate energy distribution in the radiation emitted by the Earth in the range 0 – 10 mm.
(2)
(Total 4 marks)