JPJC 2026 Wave Motion Assignment

2026/JPJC/PHYSICS/9478 1 JURONG PIONEER JUNIOR COLLEGE 9478 H2 PHYSICS WAVE MOTION ASSIGNMENT 1 [N96/P3/Q2(part)] A progressive wave passes through two points P and Q, in the direction from P to Q. The two points are separated by a distance of 0.90 m. Fig. 1.1 shows how the displacement y at point P varies with time t. Fig. 1.2 shows how the displacement of the wave at time t = 0 varies with the distance x from point P. Fig. 1.2 (a) Using data from the graphs, deduce, for this wave, (i) its wavelength, (ii) its frequency, (iii) its speed, 2.5 5.0 0 t / ms y / mm 2.0 -2.0 Fig. 1.1 P Q y / mm x / m –2 –1 2 0 1 0.2 0.4 0.6 0.8 0.9 1.0

2026/JPJC/PHYSICS/9478 2 (iv) the phase difference between point P and Q, (v) the ratio of amplitude at P to the amplitude at Q, (vi) the ratio of intensity at P to the intensity at Q. [6] (b) Light waves, sound waves in air and water waves are different forms of waves. Suggest, with a reason, which of these waves might be the wave being described by the graphs in Fig. 1.1 and Fig. 1.2. [2] ___________________________________________________________________ ___________________________________________________________________ 2 [J82/P3/Q1(adapted)] A ship’s siren vibrates with displacement y, given by ( ) ( )sin 200y t a t = , where a is a constant. The sound travels and causes the vibration of the tympanic membran e (eardrum) of an observer who is 500.00 m away. The speed of sound is 335 m s−1. (a) Calculate (i) the frequency of the sound, [1] (ii) the number of wavelengths of this sound there are between the siren and the ear drum, and [2] (iii) the phase difference between the motion of the siren and the eardrum. (Ignore any possible phase differences between vibrating surfaces and the adjacent air.) [1]

2026/JPJC/PHYSICS/9478 3 (b) The intensity of sound heard by the observer is approximately 621.0 10 W m−− . What is the intensity of sound after the ship moves 300 m directly towards the observer? [2] 3 [N2010/P3/Q7(part)] Light is polarised when it passes through a sheet of material known as polaroid. The component of the displacement of the wave in the direction of polarisation produced by the polaroid is unaffected as the wave passes through the polaroid. The component normal to the direction of polarisation is completely absorbed by the polaroid. Two sheets of polaroid P and Q are placed close to each other. Their directions of polarisation are parallel to one another, as shown in the Fig. 3.1. Fig. 3.1 A parallel beam of light passes through polaroid P. The beam, after passing through polaroid P, has amplitude A and intensity I. (a) The beam then passes through polaroid Q. For the light transmitted through polaroid Q, state (i) the amplitude (in terms of A), (ii) the intensity (in terms of I), (iii) the relationship between the answers to (i) and (ii). [3]

2026/JPJC/PHYSICS/9478 4 (b) The polaroid Q is now rotated about the axis of the light beam, as shown in Fig. 3.2. Fig. 3.2 The plane of polaroid Q remains parallel to the plane of polaroid P. The angle between the direction of polarisation of polaroid P and of polaroid Q is . Complete the table below to show the amplitude, in terms of A, and the intensity, in terms of I, for angle  equal to 180, 90 and 60. angle  amplitude intensity 180 90 60 [3]