A1. This question is about the eye and sight.
(a) Outline what is meant by additive colour mixing.
(b) The graph shows the variation with wavelength of light absorption for the red-sensitive cone cells of a normal eye.
Aibhe has colour blindness with reduced quantities of pigment in her red-sensitive cones.
(i) Sketch on the graph the light absorption curve of the red-sensitive cones for Aibhe.
(ii) State and explain the difference in the perceived colour, between Aibhe and a person with normal colour vision, when observing a magenta (purple) object in white light.
A2. This question is about radio telescopes.
A distant galaxy emits radio waves of frequency 6.0×109 Hz and is moving with speed 6.0×106 m s–1 directly away from an observer on Earth.
(a) Determine the wavelength of the radio wave as measured by the observer on Earth.
(b) The radio signals from two stars on opposite sides of the galaxy are detected on Earth using a radio telescope. The telescope has a circular receiving dish.
(i) State the Rayleigh criterion for the images of two point sources to be just resolved.
(ii) The galaxy is 2.0×1021 m from Earth and the stars are separated by 5.0×1019 m.Determine the minimum size of the telescope dish required to resolve the images of the two stars at a wavelength of 5.1×10–2 m.
A3. This question is about standing waves in a vibrating string.
A guitar string vibrates at 330 Hz in its fundamental mode.
(a) Describe the formation of standing waves in a string fixed at both ends.
(b) The length of the string is 0.64 m. Calculate the velocity of the wave in the string.
A4. This question is about polarization.
Outline how polarization may be used in stress analysis.