1 / 22

Understanding Waves, Reflection and Refraction

Understanding Waves, Reflection and Refraction. Physics Revision. In this lesson you will revisit:. The basic principles of waves. The wave formula. Reflection. Refraction and Total Internal Reflection. You need to be able to:. Describe the parts of a wave.

sharis
Télécharger la présentation

Understanding Waves, Reflection and Refraction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Understanding Waves, Reflection and Refraction Physics Revision

  2. In this lesson you will revisit: • The basic principles of waves. • The wave formula. • Reflection. • Refraction and Total Internal Reflection.

  3. You need to be able to: • Describe the parts of a wave. • Know the difference between longitudinal and transverse waves. • Use the wave equation. • Explain the processes of reflection, refraction and total internal reflection. • Know how sound waves behave and the uses of ultrasound. • Describe how seismic waves behave and what they tell us about Earth’s structure.

  4. Waves : Introduction  = wavelength Frequency is the number of waves that pass a point each second. a = amplitude Crest / Peak  a  Displacement+ Time a  Trough

  5. Transverse Waves • Most waves are transverse. • Transverse waves include light and all other electromagnetic waves, ripples on water, waves on strings and a rope being flicked up and down. • The vibrations are at 90º to the direction of travel of the wave.

  6. Longitudinal Waves • The only ones that you need to know are sound waves and earthquake p-waves. • The vibrations are along the same direction as the wave is travelling.

  7. The Wave Formula V =  x  v   f  x

  8. Reflection of Light • It allows us to see objects. • From a rough surface, like paper, light reflects in all directions – DIFFUSE REFLECTION. • When light reflects from an even surface it’s all reflected at the same angle – CLEAR REFLECTION. • Angle of incidence = Angle of reflection

  9. Refraction – a property of all waves. • This is when waves change direction as they enter a different substance. • It is caused by the change in speed of the waves. • In water waves slow down in shallower regions. • Sound waves can also be refracted.

  10. Air toPerspexangle of incidence > angle of refractioni > r • As the light ray moved from air into perspex it moved towards the normal. • If light rays move from a less dense medium (air) to a more dense medium (perspex) they ‘bend’ towards the normal. i > r

  11. Perspex toAirangle of incidence < angle of refractioni < r • As the light ray moved from perspex into air it moved away from the normal. • If light rays move from a more dense medium (perspex) to a less dense medium (air) they ‘bend’ away from the normal. i < r

  12. This angle is called the critical angle [ c] Total Internal Reflection  i <  c Refraction  i =  c Critical case  i >  c Total Internal Reflection [TIR] Different materials have different critical angles. Diamond has the lowest at 24º which is why it reflects so much light.

  13. Uses of Total Internal Reflection • Binoculars. • Periscopes • Reflectors • Optical Fibres • You will need to know the position of the prisms in binoculars and periscopes.

  14. Which wave below is a longitudinal wave? • Ultraviolet • Water • Light • Sound Which wave below is a longitudinal wave?

  15. What are the units of frequency? • Metres • Hertz metres • Hertz/metres • Hertz

  16. A wave has a wavelength of 6m and a frequency of 5Hz. What is the speed of the wave? • 1.2 m/s • 0.88 m/s • 3.0 m/s • 30 m/s

  17. Which of the following is not a light source? • The Sun • A star • Traffic lights • A book

  18. Which of the following is not seen by reflected light? • Your hand • Jupiter • Light bulb • The Moon

  19. Which of the following is the most dense? • Air • Water • Glass • Lead

  20. When light changes direction as it moves from one medium to another we call this effect what? • Reflection • Refraction • Diffraction • Total internal reflection

  21. What happens to the speed of light as it moves from air into glass? • Decreases • Increases • No effect • Decreases and increases

  22. If a ray of light moves from air to glass parallel to the normal what happens? • No change in direction • It bends away from the normal • It bends towards the normal • It stops

More Related