(a) A student listens to the sound waves produced by a car siren. When the car is stationary, the student hears a constant frequency sound. Describe how the wavelength and frequency of the sound waves heard by the student change when the car is driven away from the student.

The ‘steady state’ theory was once a popular alternative to the ‘big bang’ theory. The ‘steady state’ theory suggested that the universe, although expanding, had no origin and it has always existed. As the universe expands, a small amount of matter is created to keep the universe looking exactly the same all of the time.

The visible part of the electromagnetic spectrum from a star includes a dark line. This line is at a specific wavelength. The diagram shows the position of the dark line in the spectrum from the Sun and in the spectrum from a distant galaxy.