Waves

• Speed of sound in the air 


  330m/s
• Diagram of a transverse wave

  
• electromagnetic spectrum diagram in order

  
• radio waves are used to transmit radio signals, TV signals and mobile phone signals
• infrared is used as remote controls and night vision goggles
• microwaves are used by microwave ovens and satellite dishes
• visible light is what we see with our eyes
• ultraviolet is used to sterilise water and kill bacteria on surfaces
• x-rays are used to take x-ray images of bones and organs
• gamma rays are used in cancer treatment
• what is the electromagnetic spectrum


  The complete range of all types of radiation that has both electric and magnetic fields and travels in waves.
• transverse waves example

  • ripples on the surface of water
  • vibrations in a guitar string
  • a Mexican wave in a sports stadium
  • electromagnetic waves - eg light waves, microwaves, radio waves
  • seismic S-waves
• what are transverse waves?

  In transverse waves, particles oscillate perpendicular to the direction of energy
• what are longitudinal waves?

  In longitudinal waves, particles oscillate parallel to the direction of energy
• Examples of longitudinal waves include:

  • sound waves
  • ultrasound waves
  • seismic P-waves
• frequency (Hz): number of complete oscillations per second
• how does transverse waves link with the electromagnetic spectrum?

  all waves in the electromagnetic spectrum are transverse waves
• what is the wavelength?


   the distance between a point on one wave and the same point on the next wave. 
• what is the wave direction?

  direction the energy travels in a wave
• what is the diffrence between peak and crest

  nothing, they both mean the top of the wave
• what is the trough?

  bottom of the wave
• what is the amplitude?

  the maximum displacement of a point of a wave from its rest position.
• diagram of a longitudinal wave....

  
• what is the difference in oscillations between longitudinal and transverse waves?

  Both the transverse and longitudinal waves have different directions of oscillations. Transverse waves will have oscillations perpendicular to the direction of travel. Longitudinal waves will have oscillations parallel to the direction of travel,
• convex lense diagram

  
• how do we know that this diagram is a convex lense?


  the lights all refract to a point

  
• how are the lenses drawn (diverging is the same as concave lense)

  A) concave

  
• we know this is a concave lense since the lines of light refracted don't meet at a focal point therefore the focal point is to the left of the lens.

  
• diagram of a concave lens. as seen the focal point is to the left of the lense. this means that this is a virtual image.

  
• what is the difference between real and virtual images


  • Real image → Right side (opposite side of lens, inverted).

  • Virtual image → Left side (same side as the object, upright).
• What happens to light rays that pass through a lens?


  it is refracted
• What name is given to the distance between the lens and the principal focus/ focus point?


  the focal length
• what is the difference the terms principal focus and focal point? 


  the terms principal focus and focal point both refer to the same concept and can be used interchangeably when describing where parallel rays of light converge or appear to converge after interacting with a lens or mirror.
• the 3 correct statements are that the image is upright, enlarged and virtual

  
• in this case the image is virtual as it is on the left of the lense

  
• the image is upright, diminished and virtual

  
• Figure 9 shows a spotlight containing a convex lens. A red filter is placed in front of the spotlight. The spotlight is directed at a blue object. Figure 9 Explain why the blue object appears black.

  only red is transmitted by the filter red is absorbed by the (blue) object (so) no light is reflected by the (blue) object
• describe the differences between longitudinal and transverse waves?

  In a longitudinal wave, particles oscillate parallel to the direction of energy. In a transverse wave, particles oscillate perpendicular to the direction go energy transfer.
• what wave is the electromagnetic spectrum?

  transverse waves
• name one longitudinal wave?

  Sound wave