Light

• law of reflection

  angle of incidence(i) = angle of reflection(r)
• speed of the light in the air

  300,000 km/s
• luminous object = source of light
• black objects absorb all light = none is reflected
• incident ray = the ray that hits the surface of the object
• reflected ray = the ray that is reflected off the surface
• the angle between normal and the incident ray = angle of incidence
• the angle between normal and the reflected ray = angle of reflection
• refraction = the bending of light as it passes from one medium to another(due to different density)
• depending on how close the particles are to each other, the light can speed up or slow down
• light bends towards the normal when it slows down
• light bends away from the normal when it speeds up
• why does dispersion occur when light enters a prism?

  • when light enters a prism, it is going from one medium to another
  • light is refracted when it enters a different medium
  • dispersion happens because different colors are refracted(they have different wavelengths)
• different colors of light have different frequencies(wavelengths)
• the higher the frequency, the more the light refracts
• primary colors = red, blue and green
• secondary colors = cyan, magenta and yellow
• a filter absorbs specific frequencies of light and only lets the frequencies you want through
• red has the lowest frequency and violet has the highest frequency
• a normally green apple will look black when a torch with a red filter is used on it because :

  • the red filter absorbs all the colors of light apart from the red light
  • the apple normally looks green because it absorbs all frequencies of light apart from green light and reflects it
  • the red light is absorbed by the apple and no light is reflected into the eye to be detected
• red has the highest wavelength and violet has the lowest wavelength
• the higher the wavelength, the higher the speed