Leaving cert physics waves and refraction

  1. What is a wave
    A disturbance that carries energy from one place to another
  2. Name the two types of waves
    longitudinal and transverse
  3. Define a transverse wave plus example
    the direction of the vibration is perpendicular to the energy of the wave

    • e.g waves in water
    • radio waves
    • visible light
  4. Define a longitudinal wave plus example
    the direction of the vibration is parallel to the propagation of the wave

    • sound waves
    • compression waves on slinky
  5. Define period
    • direction of the wave
    • propagation
  6. Define electromagnetic waves
    waves that disturb or vibrate electric and magnetic fields

    m and e perpendicular to each other and direction
  7. What are the 5 wave phenomena
    • reflection
    • refraction
    • diffraction
    • interference
    • polarisation (light only)
  8. Interference
    the addition of two or more waves causing a single resultant wave
  9. Coherent waves
    two waves are said to be coherent if they have the same frequency and are in phase or have a constant phase difference between them
  10. Define "inphase"
    means that crests and crests are directly in line with each other
  11. Constructive interference
    happens when two or more waves combine to give a resultant wave with greater amplitude than the source wave
  12. Destructive interference
    Happens when waves combine and the resulting wave has a lesser amplitude than the source wave
  13. Frequency
    the number of cycles completed at any one point/second

    unit hertz (Hz)
  14. Period of a wave
    the time taken to undergo one complete cycle
  15. The amplitude of a wave
    the height of a wave
  16. wHAT IS THE CREST AND Trough
    the top and bottom of a wave
  17. Why is each fibre coated with glass of lower refractive index? 
    Because total internal reflection can only occur for rays traveling from a medium of higher to lower refractive index.
  18. Explain, with the aid of a labeled diagram, how a ray of light is guided along a fiber.
    An optical fiber consists of a glass pipe coated with a second material of lower refractive index.

    5. Light enters one end of the fibre and strikes the boundary between the two materials at an angle greater than the critical angle, resulting in total internal reflection at the interface.

    6.This reflected light now strikes the interface on the opposite wall and gets totally reflected again.

    7. This process continues all along the glass pipe until the light emerges at the far end.
  19. Diffraction
    the ability of a wave to spread out after it has encountered an obstacle when waves meet to create interference patterns
  20. Diffraction grating
    consists of transparent material with a large number of parallel lines etched on it
  21. Polarisation
    waves that vibrate only in a single plane
  22. dispersion
    which is the separating of light of the different wavelengths
  23. Refraction
    the way in which light bends when it passes from one medium to another
  24. Snell's law

    the normal angle of incidence, angle of refraction are all on the same plane
  25. Applications of optical fibers
    endoscopy and telecommunications industry
  26. Total internal relflection
    where light is reflected back from a boundary between two media when the angle of incidence is greater than the critical angle
  27. Critical angle
    the angle of incidence for which the angle of refraction in 90 degrees
  28. Power of a lens
  29. When two or more lenses are in contact
  30. Accommodation
    the process of adjusting the focal length of the lens to focus distant objects near objects clearly on the retina
  31. Myopia
    (short-sight) means distant objects can not be seen clearly
  32. Hyperopia
    (long sight) means near objects can't be seen clearly
  33. Which needs a convex lens
    • h
    • image forms behind retina
    • to focus on retina
  34. Which needs a concave lens
    • M
    • light focused infront of retina
    • concave
  35. Reflection
    the bouncing of light rays off the surfaces
  36. law of reflection
    The incident ray, the normal and reflected ray are all on the same plane

    the angle of incidence is equal to the angle of reflection
  37. Example of concave mirrors
    dentist's mirrors
  38. Example of convex mirrors
    • concealed entrances
    • supermarkets
    • car rear view mirror

    give diminished view
  39. A standing wave
    is produced when two waves of the same frequency and amplitude meed, moving in the opposite directions
  40. Harmonics
    are multiples of the natural frequency of vibration of  body
  41. Resonance
    the transfer of energy between two bodies of the same natural frequency
  42. The intensity of sound at a point
    the rate at which energy crosses a unit area perpendicular to the direction in which the sound is travelling
  43. The frequency limits of audibility
    The highest and lowest frequency sound waves that the average human can hear
Card Set
Leaving cert physics waves and refraction