Longitudinal and Transverse Waves

Transcription

1 Longitudinal and Transverse Waves

2 Learning Intentions To develop an understanding of the properties of transverse and longitudinal waves. Success Criteria You will be successful if you are able to... Draw a transverse wave and label; crest trough, wavelength, null position and amplitude. Give the symbols for wavelength and amplitude. Draw a diagram showing the direction of wave motion and direction of material motion in longitudinal and transverse waves. Define wave speed as the distance travelled by the wave per second. Solve problems with waves using the equation v=d/t

3 Wavelength λ Crest λ Null Position Amplitude (A) λ Trough Wavelength is the distance between similar points on the wave

4 Transverse Waves

5 Learning Intentions To develop an understanding of the properties of transverse and longitudinal waves. Success Criteria You will be successful if you are able to... Draw a transverse wave and label; crest trough, wavelength, null position and amplitude. Give the symbols for wavelength and amplitude. Draw a diagram showing the direction of wave motion and direction of material motion in longitudinal and transverse waves. Define wave speed as the distance travelled by the wave per second. Solve problems with waves using the equation v=d/t

6 Transverse Waves Motion of the material Direction of Travel In a transverse wave the substance moves perpendicular to the direction of motion of the wave. Transverse Wave Animation Animation courtesy of Dr. Dan Russell, Grad. Prog. Acoustics, Penn State

7 Longitudinal Waves Direction of Travel Motion of the material In a longitudinal wave the substance moves parallel to the direction of motion of the wave. Longitudinal Wave Animation Animation courtesy of Dr. Dan Russell, Grad. Prog. Acoustics, Penn State

8 Learning Intentions To develop an understanding of the properties of transverse and longitudinal waves. Success Criteria You will be successful if you are able to... Draw a transverse wave and label; crest trough, wavelength, null position and amplitude. Give the symbols for wavelength and amplitude. Draw a diagram showing the direction of wave motion and direction of material motion in longitudinal and transverse waves. Define wave speed as the distance travelled by the wave per second. Solve problems with waves using the equation v=d/t

9 Reminder - Distance, Speed and Time Formula Wave speed meters per second m/s or ms -1 Distance travelled by the wave (meters - m) Time (seconds - s )

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11 Lesson 2 Frequency

12 National 4

13 v National 4 1 Hertz Wave Fixed point Frequency 0 waves Counter 0s0 Timer

14 v National 4 1 Hertz Wave Frequency 1 wave Counter 1s0 Timer

15 v National 4 1 Hertz Wave Fixed point Frequency 2 waves Counter 2s0 Timer

16 Lesson 3 Frequency from a Graph and consolidation

17 National 4

18 Finding Frequency from a Graph Amplitude (m) time (s)

19 National 4

20 Diffraction

21 Learning Intentions To develop an understanding diffraction of waves. Success Criteria Will have observed and sketched diagrams of the diffraction of waves in some simple situations. Will be able to give a definition of diffraction Will be able to describe examples of diffraction occurring with radio waves. State the relationship between wavelength and size of the diffraction which occurs. National 4

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23 Diffraction through a gap Short Wavelength Diffraction through a gap Long Wavelength The wavelength, frequency and speed are same before and after diffraction. The only change is the direction in which the wave is travelling. The diffraction effect is greatest when the width of the gap is about the same size as the wavelength of the wave.

24 Diffraction of Radio Waves

25 Short Wave Diffraction Diffraction around an obstacle Short Wavelength Long Wave Diffraction Diffraction around an obstacle Long wavelength TV and FM Radio Signals have a wavelength of around few metres (microwaves) which allow for higher data transmission. However this means they cannot diffract over or around hills. Long-wave radio is transmitted using waves with a wavelength of around 1km. This means they can diffract around objects including hills and buildings; they can reach places that short-wave radio cannot. This is why it is often possible to listen to long wave radio stations such as radio 4, even when FM reception is poor.

26 Telescopes cameras National 5 Refraction Binoculars Microscopes

27 Learning Intentions To explore the refraction of light. Success Criteria You will be successful if you can... Explored what happens to a ray of light as it passes into and out of a glass block at different angles. Use correctly the terms Angle of incidence. Angle of refraction. Normal Explain refraction in terms of change of wave speed.

28 Ray Diagram How do you draw a ray diagram?

29 Ray Diagram You will need: Power Supply (12V) Ray box Rectangular Prism Paper Sharp Pencil Ruler Put your bag under your desk

30 Refraction in Action Can you explain how objects appear to separate underwater?

31 Ray Diagram Angle of incidence Angle of refraction Normal Normal Angle of incidence Angle of refraction Refraction is the change in the direction of light when it moves from one material to another due to the light changing speed.

32 Remember FAST Faster Away Slower Towards When light travels into a LESS dense material it s speed increases and the light rays bend AWAY from the normal When light travels into a MORE dense material it s speed decreases and the light rays bend TOWARDS the normal

33 Appear to Disappear Willebrord Snellius studied the laws of refraction in the 17th Century. A materials refractive index describes how light travels through the material. Light will travel through materials at the same speed if they have the same refractive index

34 ??Question time?? The ray diagram shows light moving from air into glass.write an explanation of why the ray moves in such a way. Include these words: refraction, incident ray, refracted ray, denser, towards or away and medium. Glass Air

35 Learning Intentions To explore the refraction of light. Success Criteria You will be successful if you can... Explored what happens to a ray of light as it passes into and out of a glass block at different angles. Use correctly the terms Angle of incidence. Angle of refraction. Normal Explain refraction in terms of change of wave speed.

36 Refraction Explained Refraction/change in speed link

37 Lesson 2 Critical angle and total Internal reflection

38 Telescopes Critical angle and cameras total Internal reflection Binoculars Microscopes

39 Learning Intentions To explore the refraction of light. Success Criteria You will be successful if you can... State what happens to a refracted ray when moving from glass to air. State that above the critical angle total internal reflection occurs. Be able to give an example of the practical use of total internal reflection.

40 Ray Diagram Angle of incidence Angle of refraction Normal Normal Angle of incidence Angle of refraction Refraction is the change in the direction of light when it moves from one material to another due to the light changing speed.

41 Total Internal Reflection Describe what happens when this angle is increased.

42 Making Optical Fibres Video Applications of Total Internal Reflection Heartburn and Acid Reflux Testing - Endoscopy Corning Optical Fibre video (Detailed but difficult)

43 Total Internal Reflection

44 Ultimate Physics Pg18