In a laboratory, the spectrum of atomic hydrogen has a wavelength of 656.61 nm. The spectrum of a star observed on Earth is found to have the same line in the spectrum shifted to 656.54 nm.
(b)
(i)
Calculate the speed of the star relative to the Earth.
[2]
(ii)
Explain whether the star is moving towards or away from the Earth.
A scientist is conducting an experiment on bees. They set up monitoring equipment near a hive, including a microphone which picks up the buzz from individual bees flying past.
A single bee flies at a constant speed in a straight line past the microphone, and the frequency of the buzz is detected.
(a)
Explain the sound pattern detected by the microphone as the bee moves towards and away from the microphone.
When bees are about to swarm, they produce a higher pitched buzz, known as 'piping'. The frequency of the piping sound is 550.0 Hz. The scientist moves the microphone closer to the hive during this process. Whilst they are moving the change in observed frequency is 3.4 Hz.
(c)
(i)
Determine the speed at which the scientist walks towards the hive.
[3]
(ii)
Explain the effect of any assumptions made in determining this speed.
An ambulance siren emits two pure sounds. The lower of the two sounds has a frequency of 650 Hz. It is travelling towards a stationary observer at 13.4 m/s. The speed of sound in air is 340 m s−1.
(a)
Calculate the change in frequency, Δf,between the source frequency and that heard by the observer.
As the ambulance approaches a red light at which a number of cars are stopped, it changes its siren to a single monotone sound which the car drivers observe as 700 Hz. The ambulance slows further to 5.3 m s−1.
(c)
Calculate the wavelength of sound emitted by the ambulance.
The ambulance pulls to a stop but continues to emit the 700 Hz tone. A car passes the ambulance. As it moves away the sound heard by the car driver has a frequency of 682 Hz.
(d)
Determine the speed of the car as it drives away from the ambulance
The diagram shows a stationary wave source, R, in water. The source produces waves with a constant frequency. The distance between each successive wavefront is equal to the wavelength of the waves produced by R.
The speed of the waves in water is v.
(a)
Sketch three successive wavefronts produced when the source is moving to the right at a speed of 0.75v.
Every year, an alien species holds a race between two teams. One of the teams has green lights on its spaceships and the other has purple light. During the race the two ships approach a space station.
From the point of view of the space station commander, on the space station, the two colours appear to be identical. as the ships approach the station.
(a)
Explain how the commander knows which spaceship is travelling faster.
The wavelength of light from the purple ship is 420 nm and from the green ship is 550 nm. The observed frequency of both ships from the space station is 405 nm.
(b)
(i)
Determine the speed of the purple ship.
[2]
(i)
Determine the ratio of speeds between the two ships.
The green space ship enters the atmosphere of a planet near the spaceship for the victory ceremony, which has amassed a large crowd. It slows down to 0.005% of its speed during the race. As it nears the surface it emits a continuous tone of frequency 2320 Hz. The speed of sound in the atmosphere of this planet is 5690 m s−1.
(c)
Calculate the frequency of sound observed by the crowd.
The space station also has the capacity to detect light from other galaxies. In a laboratory, the frequency of electromagnetic radiation from a distant galaxy has been redshifted by 4.2 × 109 Hz. In the laboratory, the same light has a frequency of 1.9 × 1012 Hz.
(d)
(i)
Calculate the speed of recession of the galaxy.
[1]
(ii)
Discuss the implications of the recession of the galaxies in the universe.
