Physics Topic 6: Waves

22 flashcards · Physics · by Marli Williams

  1. What do all bodies do?

    Emit and absorb infrared radiation.

  2. Transverse Wave

    Waves where the points along its length vibrate at 90 degrees to the direction of energy transfer.

  3. What does the intensity and wavelength distribution of an emission depend on?

    The temperature of the body.

  4. At what rate does a body at constant temperature absorb radiation?

    At the same rate as it is emitting radiation.

  5. Properties of a Transverse Wave

    Energy transfer is perpendicular to wave motion Only transfers energy Only moves in solids and on the surfaces of liquids Some transverse waves (electromagnetic waves) can move in solids, liquids and gases and in a vacuum.

  6. What happens to the temperature of a body when it absorbs radiation faster than it emits it?

    It increases.

  7. Examples of Transverse Waves

    Ripples on the surface of water S-waves EM waves

  8. Longitudinal Wave

    Waves where the points along its length vibrate parallel to the direction of energy transfer. They have areas of RAREFACTION and COMPRESSION

  9. What does the temperature of Earth depend on?

    The rate of absorption and emission of radiation Reflection of radiation into space

  10. Properties of a Longitudinal Wave

    Energy transfer is parallel to wave motion Only transfers energy Moves in all states (except vacuum) Have key points of rarefaction (far apart) and compression (close together)

  11. Examples of Longitudinal Waves

    Sound waves P-waves Pressure waves caused by repeated movements in a liquid or gas

  12. What is a perfect black body?

    An object that absorbs all of the radiation incident on it.

  13. What does a black body not do?

    It does not reflect or transmit any radiation.

  14. Relationship between the temperature of a body and radiation.

    The temperature of a body is related to the balance between incoming radiation absorbed and radiation emitted. Example: The Greenhouse Effect More Radiation is being absorbed by the Earth then emitted causing the Earth's temperature to increase.

  15. Why do waves travel but not the water or air they travel through?

    Water Ripples: Observe waves spreading out on water after a small object is dropped in - the waves travel across the surface but the water does not travel away from the object Sound Waves: Observe a tuning fork vibrating so that sound waves travel through the air away from it - the air does not travel away from the object as if it did a vacuum would be created

  16. What would be the the best possible emitter? Why?

    A perfect black body. Since a good absorber is also a good emitter and a black body absorbs all radiation.

  17. Amplitude of a wave

    The maximum displacement of a point on a wave away from its undisturbed position.

  18. Wavelength of a wave

    The distance from a point on one wave to the equivalent point on the adjacent wave.

  19. Frequency of a wave

    The number of waves passing a point each second. Unit: Hertz (Hz)

  20. Period Equation

    Period = 1/frequency Unit: Seconds (s)

  21. What happens to infrared radiation given out as a body becomes hotter?

    The hotter the body, the more infrared radiation it radiates in a given time.

  22. Wave Speed

    The speed at which the energy is transferred (or the wave moves) through the medium. Wavespeed = Frequency x Wavelength