Lesson 1-F5 Physics_a1

Main Office: No. 25-01, 35-01 Jalan Austin Heights 3/1, Taman Mount Austin (Tel: 073616538)Branch: No. 15A, 17A, 21A & 41A Jalan Indah 16/12, Taman Bukit Indah (Tel: 07-2349168)

Name : Subject : Chapter :

SPM Physics Waves

Teacher: Class : Lesson No :

Topic :

1.1 Understanding Waves

Date : Time :

Cheng Wui Leap F5 Physics 1

Scheme of Assessment PAPER 1 2

3

TYPE MCQ [50Qs] Section A [8 Qs](60m) Section B [9,10][choose 1][20m] Section C[11, 12][Choose 1][20m] Section A [ 2Qs] [28 m] Section B[3,4] [Choose 1] [12m]

DURATION 1 hr 15 minutes 2 hr 30 minuts

MARKS 50 100

1hr 30 minutes

40

Form 5 Chapter Waves

Electricity

Electromagnetism

Electronics

Topic 1.1 Understanding Waves 1.2 Analysing Reflection of Waves 1.3 Analysing Refraction of Waves 1.4 Analysing Diffraction of Waves 1.5 Analysing Interference of Waves 1.6 Analysing Sound Waves 1.7 Analysing Electromagnetic Waves 2.1 Analysing Electric Fields and Charge Flow 2.2 Analysing the Relationship between Electric Current and Potential Difference 2.3 Analysing Series and Parallel Circuits 2.4 Analysing Electromotive Force and Internal Resistance 2.5 Analysing Electrical Energy and Power 3.1 Analysing the Effect of a Current-carrying Conductor 3.2 Understanding the Force on a Current-carrying Conductor in a Magnetic Field 3.3 AnalysingElectromagneticInduction 3.4 Analysing Transformers 3.5 Understanding the Generation and Transmission of Electricity 4.1 Understanding the Uses of the Cathode-Ray 1

Oscilloscope (CRO) 4.2 Understanding Semiconductor Diodes 4.3 Understanding Transistors 4.4 Analysing Logic Gates Radioactivity

5.1 Understanding the Nucleus of an Atom 5.2 Analysing Radioactive Decay 5.3 Understanding the Uses of Radioisotopes 5.4 Understanding Nuclear Energy 5.5 Realising the Importance of Proper Management of Radioactive

1.1 Understanding Waves

1. An oscillating or vibrating motion in which a point or body moves back and forth along a line about a fixed central point produces waves. 2. An oscillating or vibrating system acts as the source of waves which transfer energy from one point to another (without transferring mass). 3. Examples of waves: (a) Light waves are produced as a result of vibrations of electrons in an atom. 2

(b) Sound waves are produced by vibrating mechanical bodies such as guitar strings or a tuning fork. (c) Water waves are produced by a disturbance (or vibration) on a still water surface.

Propagation (Travelling) of Waves 1. When a wave travels through a medium, the particles of the medium vibrate about their equilibrium positions. 2. However, the particles of the medium do not travel in the direction of the wave. 3. A wave transfers energy and the momentum from the source of the wave (the oscillating or vibrating system) to the surroundings.

Activity To To demonstrate that waves transfer energy without transferring matter Apparatus/ Materials Radio, candle and matches. Procedure

1. A candle is placed about 10 cm from the speaker of a radio. 2. The candle is lit and the movements of its flame is observed. 3. Then, the radio is turned on and the volume of the sound is gradually increased until a change in the movement of the flame becomes noticeable. Discussion The flame vibrates when the radio is turned on. This observation shows that the propagation of the sound waves from the vibration of the cone of the speaker transfers energy (or momentum) to the flame and causes it to vibrate. Conclusion Waves transfer energy from a vibrating system without transferring matter. The total energy carried by a wave depends on its amplitude and frequency. A wave with a large amplitude or a high frequency carries a larger amount of energy.

Wavefronts in Relation to the Direction of Propagation of Waves

3

1. A wavefront is a line or plane on which the vibrations of every points on it are in phase and are at the same distance from the source of the wave. 2. Points in a wave are in phase if they vibrate in the same direction with the same displacement. Plane Wavefronts 1. Figure 1.4 shows the production of plane water waves when a wooden bar vibrates vertically at a constant frequency on the surface of the water

2. Lines PQ, RS, TU and VW are straight lines along the respective crests of the waves. These lines are called wavefronts. 3. Figure 1.5 shows that the wavefronts are perpendicular to the direction of propagation.

Circular Wavefronts 1. When we use a fingertip to touch the surface of water repeatedly, circular wavefronts are produced as shown in Figure 1.6.

2. The wavefront at any point is perpendicular to the direction in which the wave is advancing Types of Waves There are two types of waves.

(a) (b)

Transverse wave Longitudinal wave 4

Transverse Waves 1. A transverse wave is a wave in which the vibration of particles in the medium is at right angle (perpendicular) to the direction of propagation of the wave.

2.

Examples of transverse waves are water waves and light waves.

Longitudinal Waves 1. A longitudinal wave is a wave in which the vibration of particles in the medium is parallel to the direction of propagation of the wave.

2. Example of longitudinal waves are sound waves. Exercise 1. [SPM’06/Q31]Diagram 18 shows the cross section of water waves.

Which of the following statements is true about the water waves? A T and U have the same phase B Wave energy is transferred from position S to U C The wavelength is the distance between S and U D The particle at U oscillates in a direction parallel to the direction of the wave propagation

5

2.

[SPM’06/Q35]Diagram 22 shows two situations where a ball floats and moves on the surface of the water.

The direction of the movement of the ball is A parallel to the direction of the wave propagation B perpendicular to the direction of the wave propagation C the same as the direction of the wave propagation D the opposite to the direction of the wave propagation 3. [SPM’09/Q29]Which diagram shows the production of a longitudinal wave?

4. [SPM’10/Q25]Which device is used to show that light is a transverse wave? A Glass prism B Double slit C Diffraction grating D Polaroid bloc 6

5. [SPM’07/P2/Q1]Diagram 1 shows how a vibrating tuning fork produces sound waves in air.

(a) Underline the correct answer in the bracket to complete the sentence below. Sound wave is a (longitudinal, transverse) wave.[1 mark]

(b) Based on Diagram 1, (i) name region X, [1 mark]

(ii) mark one distance which is equal to a wavelength of the sound waves. Label the distance using the symbol A.[1 mark]

(c) The tuning fork in Diagram 1 vibrates in water. What happens to the speed of sound?[1 mark]

6. [SPM’08/P2/Q1]Diagram 1 shows a slinky spring being moved left and right continuously.

(a) Complete the sentence below by ticking (✓) the correct box.

7

(b) On Diagram 1, mark 'X' on any one of the crests of the wave.[1 mark] (c) Complete the following sentence by underlining the correct phrase in the bracket. [1 mark]

(d) What is transferred by the wave? [1 mark] Amplitude, Period and Frequency of a Wave 1. The amplitude, A, of a vibrating system is the maximum displacement from its equilibrium position.

2. The period, T, of a vibrating system is the time taken to complete an oscillation. The SI unit of period is second. 3. The frequency, f, is the numberof complete oscillations made by a vibrating system in one second. The unit of frequency is hertz (Hz) or s-1.

4. From the formulae of T and f , the relationship between period, T and frequency, f is:

8

T

1 f

T is inversely proportional to f and vice versa. Exercise 1. A mass on a spring oscillates with a frequency of 4 Hz. What is the time taken by the mass to complete 120 oscillations?

2. A mass on a spring oscillates with a frequency of 3 Hz. Calculate (a) the number of oscillations in 10 s,

(b) the period of oscillation.

3. A wave of frequency 240 Hz has a wavelength of 6 m. What is the speed of the wave?

Displacement-time Graph of a Wave

From the graph of s against t in Figure 1.10, the following information is obtained. (a) Amplitude, A = a cm (b) Period of oscillation, T is the time between points: (i) 0 and F, (ii) C and G or (iii) P and Q Exercise 1. 9

From the graph, (a) state the amplitude, (b) calculate the period of the oscillation, (c) calculate the frequency of the oscillation.

Displacement-distance Graph of a Wave



1. The wavelength, is the distance between successive points of the same phase in a wave. For example: (a) the distance between two successive crests or two successive troughs in a water wave, (b) the distance between two successive compressions or two successive rarefactions in a sound wave.



2. The SI unit of wavelength, is metre (m).

Exercise

10

1.

Find (a) the amplitude, (b) the wavelength of the wave.

2. The figure shows the form of a transverse wave produced by a slinky soring.

What is

(a) its amplitude? (b) its wavelength?

Relationship between Speed (v), Wavelength (



) and frequency (f)

v f Exercise 1. The displacement-distance graph in Figure 1.14 shows the motion of a transverse wave. The source of the wave produces 10 complete waves in one second.

11

Calculate (a)the amplitude, (b) the wavelength, and (c)the speed of the wave.

2. The figure below is the displacement-time graph of a wave.

Calculate

(a) the amplitude, (b) the frequency, (c) the wavelength, if the speed of the wave is 8 cm s-1. 3. [SPM’07/Q30]Diagram 19 shows a load being oscillated on a spring.Based on Diagram 19, which of the following displacement-time graphs represents oscillation of the load from P to Q and back to 0?

12

4. [SPM’08/Q29]Diagram 17 shows the displacement-distance graph of a wave. The frequency of the wave is 5.0 Hz.

What is the velocity of the wave? A 50 cm s-1 B 75 cm s-1 C 100 cm s-1 D 150 cm s-1 5. [SPM’10/Q28]Diagram 22 shows a wave.

The speed of the wave is 4.0 m s-1. The distance of 5 consecutive crests is 8 m. What is the frequency of the wave? A 0.4 Hz B 0.5 Hz C 2.0 Hz D 2.5 Hz

6.

[SPM’11/Q29]Diagram 20 shows sound waves produced by a tuning fork. The velocity of the sound in air is 340 ms-1.

What is the frequency of the sound wave? A 204.0 Hz B 283.3 Hz C 341.2 Hz D 408.0 Hz

.

13

7. [SPM’05/Q35]The graphs show the cross-sections of water waves. Which wave has the greatest energy?

8. [SPM’05/Q32]The diagram shows a wavefront pattern produced by a dipper vibrating at a frequency of 12 Hz in a ripple tank. What is the speed of the waves? A 2 cm s-1 B 8cms-1 C 12 cms-1 D 18 cms

9.

[SPM’07/Q29]Diagram 18 shows a wave pattern on water.

Wavelength is the distance between the points A P and Q

B P and R

C Q and S

D R and S 14