AQA AS Physics P4 Waves Kerboodle Answers

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C4.1 Waves and vibrations AQA AS P4 Waves Kerboodle Answers: Page No. 53

1.Answer a Transverse b Transverse c Longitudinal d Transverse 4.Ans- Polarization, also called wave polarization, is an expression of the orientation of the lines of electric flux in an electromagnetic field ( EM field ). Polarization can be constant — that is, existing in a particular orientation at all times, or it can rotate with each wave cycle. Polarization is important in wireless communications systems.

4.2 Measuring waves AQA AS P4 Waves Kerboodle Answers : Page No. 55

1 .Ans- a 0.10 m b 1800 Hz. 1.9 x 10^-2 m 2.Ans- a 0.030m 10 GHz b 600 nm. 5.0 x 10¹⁴ Hz 3.Ans-1.0 V, 1.0 kHz 4.Ans- a i) Amplitude= 8 mm, wavelength = 47 mm ii 180° iii 270° b +8mm

4.3 Wave properties 1 AQA AS P4 Waves Kerboodle Answers: Page No. 57

1Ans-. 2.Ans- a2.5s b 4.0 s after the wavefront was produced at P 3.Ans- 4.Ans- aWidening the gap without changing the wavelength b increasingthewavelength of the water waves without changing the gap width cincreasing the wavelength of the water waves and reducing the gap width dwidening the gap and increasing the wavelength of the waves? 4.4 Wave properties 2: Page No. 59 1.Ans- a when the two waves are passing through each other b when the two waves have passed through each Other. 2.Ans- a.Ans-More interference pattern occur when two dippers are moved further apart. b. Less interference occur if the frequency of the waves produced by the dippers is reduced. 3.Ans- a the receiver is moved in a line parallelto the metal plates, b the slit is then made narrower? 4.Ans-   b. There is a series of constructive and destructive interference occurring, where the wavelength is going from maxima to minima.

4.5 Stationary and progressive waves AQA AS P4 Waves Kerboodle Answers : Page No. 61

1.Ans- a b.Ans- 8.0m 2.Ans a 2.0m b.Ans i A 180° ii B 225° iii C. 0 3.Ans-a 30mm

4.6 More about stationary waves on strings AQA AS P4 Waves Kerboodle Answers: Page No. 63

1.Ans- a 1.6m b 410ms^-1 2.Ans- a0.4m b 384 0.53m 3.Ans-a 2.4 x 10^-4 kg m^-1 b 0.20 mm

4.7 Using an oscilloscope AQA AS P4 Waves Kerboodle Answers: Page No. 65

1.Ans- a i )5.0 Vcm^-1 ii 2.4cm b i1.63V ii 1.15V 2.Ans: a 22ms

45.5 Hz 3.Ans-a 12.5 V, 8.8 V b. 10 ms, 100Hz 4.Ans- A straight horizontal line 2.0 cm above thecentre line would be seen. The waveform seen on the screen has a peak height above the centre of 2.83cm and 1.5 cycles would appear on the screen. Banner 8

Practice questions: Page No. 66-67

1Ans-  (a) (i) 409 mm (ii) 12 mm (b). (i). If f is inversely proportional to L, then f L should be the same (provided the tension is not changed). At 256 Hz, f L = 210 Hz m;at 510 Hz, f L = 209 + 6 Hz m. The measurements support the hypothesis. (ii) Without changing the tension, use different tuning forks of known frequency to find the length of wire that gives the same frequency.

• For each frequency f, make several measurements of L and calculate the mean value for each length.
• Plot a graph of frequency against 1/length.
• The graph should be a straight line through the origin if f is inversely proportional to L.

2 (a) Use of c = f λ gives speed

• c = 29 × 10³ × 5.3 × 10^-2
• = 1540 m s^-1

(b) Distance travelled by the wave between transmission and detection

• = c t = 1540 × 0.23 = 354 m
• ∴ Depth of water = 1/2 × 354 =180 m (to 2 significant figures)

3 (a) (i) Longitudinal waves:particle vibration or oscillation is same as direction of propagation or energy transfer (ii) Transverse waves: Particle vibration or oscillation is perpendicular to direction of propagation or energy transfer (b) As the polarising filter is rotated through 360° the intensity transmitted will vary between maxima and minima (or light and dark) There will be two maxima (and two minima) in each 360° rotation 4Ans-. (a) Transverse waves can be polarised (b) E.g. waves on strings, waves on the surface of water, any type of electromagnetic wave (c)

• In transverse waves the vibrations take place perpendicular to the direction of energy transfer
• In longitudinal waves the vibrations take place in the same direction as the energy transfer
• Polarisation restricts the vibrations to one plane by absorbing the vibrations at right angles to this plane
• Longitudinal waves cannot be polarised because the vibrations have to take place for energy to be transmitted

5.ANS- (a) A longitudinal wave (b) BB’: an arrow to the left CC’: an arrow to the right Both arrows the same length as AA’ (or length of AA’ > BB’ > CC’) 6.Ans- (a) Wavelength = 0.80 m (b) (c)  (a) (b)

• stationary waves are formed in air by the superposition of two waves
• these are the wave travelling towards the wall and its reflection from the wall
• minima are formed by destructive interference at points where the two waves are continuously in antiphase

8 .Ans- (a)

• The effect is caused by interference (or superposition) between waves
• The two waves interfering have the same frequency (or wavelength)
• Waves are reflected from the plate
• The waves travel in opposite directions
• Maxima are produced at points where the waves are in phase (or interfere constructively)
• Minima are produced at points where the waves are in antiphase
• There is a stationary wave (or nodes and antinodes) in the region of the detector

(b) (i) (ii)

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