A1. This question is about the eye.

(a) State, with reference to the definitions of near point and far point, what is meant by accommodation.

(b) Explain how accommodation is achieved by the eye.


A2. This question is about diffraction and resolution.

(a) A parallel beam of monochromatic light is incident on a narrow rectangular slit. After passing through the slit, the light is incident on a distant screen.

Point X is the midpoint of the slit.

(i) On the axes below, sketch a graph to show how the intensity of the light on the screen varies with the angle θ shown in the diagram.

(ii) The wavelength of the light is 520 nm, the width of the slit is 0.04 mm and the screen is 1.2 m from the slit. Show that the width of the central maximum of intensity on the screen is about 3 cm.

(Question A2 continued)

(b) Points P and Q are on the circumference of a planet as shown.

By considering the two points, outline why diffraction limits the ability of an astronomical telescope to resolve the image of the planet as a disc.


A3. This question is about standing waves and organ pipes.

(a) State one way in which a standing wave differs from a travelling wave.

(b) An organ pipe of length L is closed at one end. On the diagrams, draw a representation of the displacement of the air in the pipe when the frequency of the note emitted by the pipe is the

(i) fundamental (first harmonic) frequency f1.

(ii) second harmonic frequency f2.

(c) Use your answer to (b) to deduce an expression for the ratio f1/f2.

(d) State, in terms of the boundary conditions of the standing waves that can be formed in the pipe, the reason why the ratio of the higher frequencies of the harmonics to that of the fundamental must always be an integer number.




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