physics yr 9

• waves transfer energy without transferring matter
• 2 different types of waves : mechanical and electromagnetic waves
• mechanical waves are vibrations which travel through a medium
• electromagnectic waves no medium is needed
• Transverse waves are waves that oscillate perpendicular to the direction of energy transfer.
• Longitudinal waves have a vibrating particle that oscillates parallel to the direction of the wave.
• mechnaical waves can be transverse or perpendicular
• label

  A) wavelength

  B) amplitude

  C) one complete wave

  D) trough

  E) peak

  
• laveo

  A) longitudinal wave

  B) wavelength

  C) amplitude

  D) compression

  E) rarefaction

  F) compression

  
• the amplitude of a wave is the maximum displacement of a point on the wave from its undisturbed position
• the bigger the amplitude the more energy the waves carry
• the wavelength of a wave is the distnace from a point on the wave to equivalent point on another wave
• frequency - the number of waves passing a point per second, measured in hertz (Hz)
• period - the time taken for each wave to pass a fixed point
• label

  A) 1

  B) frequency

  
• speed of a wave is the distance travelled by each wave per second
• labep

  A) wave speed

  B) frequency

  C) wavelength

  
• reflection of a wave is the change of direction of propagation of a wave when it meets a boundary
• each ripple is called a wavefront
• the incident wave is at the same angle as the reflected wave from the barrier
• refraction of waves is the change of the direction in which they are travelling when they cross a boundary between one medium and another medium
• the refracted wavefronts are closer together and and are at smaller angle to the boundary than the incident wavefront
• when crossing a boundary the wave experiences a change in speed, direction but not frequency so the wavelength changes
• electromagnetic waves are electric and magnetic disturbances that can transfer energy from a source to an absorber
• label

  A) frequency

  B) radio waves

  C) microwaves

  D) infrared

  E) visible light

  F) UV rays

  G) x-rays

  H) gamma rays

  I) wavelength

  J) energy

  
• All electromagnetic waves travel at the speed 3 x 10^8 m/s
• label

  A) wavespeed

  B) frequency

  C) wavelength

  
• The energy of the waves increase as the frequency increases
• light from ordinary lamps and the sun is called white light
• white light has all the colours of the visible spectrum in it
• all objects emit infrared radiation
• the hotter an object the more infrared radiation it emits
• infrared radiation is absorbed by our skin
• infrared radiation can damage, burn or kill skin cells because it heats up the cells
• optical fibres in communications use infrared radiation
• remote control handsets for TV and video equipment transmit signals carried by infrared radiation
• infrared scanners are used in medicine to detect infrared radiation emitted from the hotspots on the body's surface. These hot areas can mean the tissue underneath is unhealthy
• infrared cameras are used to see people in the dark
• infrared radiation ca be used to heat up objects quickly
• satellite Tv's use microwaves