visible light

• visible light is made from a range of colours. each colour has its own narrow range of wavelengths and frequencies. violets down at 400nm and reds at 700nm
• when all different colours are mixed, it creates light
• opaque objects cannot transmit light. when visible waves hit them, they absorb some wavelength of light and reflect others
• the colour of an opaque object depends on which wavelength of light are most strongly reflected, the rest are absorbed
• white objects reflect all of the wavelengths of visible light equally
• black objects absorb all wavelength of visible light
• transparent and translucent objects transmit light
• colour filters are used to filter out different wavelengths of light so that only certain colours and transmitted - the rest are absorbed
• a primary colour filter only transmits that colour. in a blue filter if white light is shown, only blue light will be let through, the rest are absorbed
• filters that are not for primary colours let through both the wavelengths of light for that colour and the wavelengths of the primary colours that can be added together to make that colour
• if an object is red, we see it as red as when the spectrum of colours hit it, all colour are absorbed except for red, which is reflected off the object and into the eye
• White light can be split up into a spectrum of these colours using a triangular block of glass or acrylic, known as a prism.

  Light is refracted when it enters the prism, and each colour is refracted by a different amount. This means that the light leaving the prism is spread out into its different colours, a process called dispersion.
• the order of the spectrum from longest wavelength to shortest wavelength is red, orange, yellow, green, blue, indigo, violet.
• wavelengths

  blue - around 400

  green - in the middle

  red- around 600-700
• Filters transmit some colours of light and absorb other colours of light.

  • Colours which are transmitted pass through the filter and come out the other side.
  • Colours which are absorbed do not pass through the filter.
• If yellow light shines at a red filter, red light passes through the filter. This is because:

  • yellow light is a combination of red light and green light
  • the red light is transmitted
  • the green light is absorbed
• Red, green and blue filters each transmit a single primary colour. Any other colours present in the light are absorbed.

  • A red filter only transmits red light. It absorbs blue light and green light.
  • A blue filter only transmits blue light. It absorbs red light and green light.
  • A green filter only transmits green light. It absorbs red light and blue light
• colours to remember