Chapter 13 MCQ  1. D (fact)  2 B (direction of vibration and wave motion is parallel, compression and rarefaction can be seen – longitudinal wave)  3 C (Draw the wave for the next instance, compare the positions) MCQ  4 B (speed = frequency x wavelength) 5 D 6 C Section B  1a) Transverse wave  1b) Transverse wave travel perpendicular to the direction of vibration, whereas longitudinal waves travel parallel to the direction of vibration  1c) Both types of waves transfer energy from one point to another without physically transferring the medium the waves travel in. Section B  1d) Transverse waves: light waves  Longitudinal waves: sound waves  2a) The wavelength of a wave is the shortest distance between any two points on the wave that are in phase.  The amplitude of a wave is the maximum displacement of a point on the wave from its rest position. Section B  2c) Speed = 0.83 m/s, wavelength = 0.2 m  Frequency = speed/wavelength = 4.2 Hz 3ai) The period of a wave is the time taken to produce one complete wave. 3aii) Time taken to travel half a wavelength = 2s. Period of wave T = time taken to travel one wavelength = 4s Section B  3b) Since the wave travels half a wavelength (4m) in 2 s,  Speed = distance / time = 4/2 =2 m/s  4a) 30 cm  4b) 4 m  4ci) frequency = 1/T = 2.0 Hz Section B  4cii) The particle moves down past the rest position until it reaches maximum displacement in the negative direction. It then moves up and reaches the rest position at t = 0.375s. (explanation: the period of the wave is 0.5 s. After 0.375 s, the wave would have moved ¾ cycle)  4ciii) At t=3.25s, the particle would have oscillated for 6.5 more complete oscillations. (3.25/0.5). Hence, the particle is half a cycle out of phase, it will be at -30 cm.  5a) 2  5b)iii) 4 Section B  5bi) Frequency = speed/wavelength = 0.4/(0.02) = 20 Hz  5bii) Period = 1 /f = 1/20 = 0.05 s Section C  1ai) Speed  = frequency x wavelength  = 2 x 0.5 = 1cm/s  1aii) wavelength  = speed/frequency  1/ 2.5 = 0.4 cm Section C  2ai) A wavefront is an imaginary line on a wave that joins all adjacent points that are in phase.  2aii) A bright zone indicates a set of waves near a crest. A dark zone indicates the a set of wavefronts near a trough.  2bi) 4 2bii) 10 Section C  2c) Region A,  speed = frequency x wavelength  =2 x 5.5 = 11.0 mm/s  Region B,  speed = frequency x wavelength  =2 x 2 = 4.0 mm/s Section C  2d) As the waves move from region A to region B, their wavelength shortens from 5.5 mm to 2.0 mm. According to the formula v = f x λ, their speed decreases from 11mm/s to 4m/s. Their frequency remains unchanged as the frequency of the dipper does not change. Data Based Question  3ai) Point E and M  3aii) Point A, I and Q.  3b) Amplitude = (6.6 – 6.2)/2 =0.2m  3ci) Frequency = 1/T = ¼ = 0.25 Hz.  3cii) Wavelength = distance between 2 consecutive points that are in phase (between the 2 trough) = 8m. Data Based Question  3ciii) Speed = 0.25 x 6 = 1.5m/s.  3d) Transverse wave.