Sensitivity of the Eye

• What are the light-sensitive cells in the eye called?

  Photoreceptors
• What do rods and cones do when they detect light?

  Convert light into electrical signals
• What happens to the chemical pigments in rods and cones when light falls on them?

  They are bleached
• How do rods and cones send signals to the brain?

  Via the optic nerve

  
• What role does vitamin A play in the function of rods and cones?

  It resets/unbleaches the cells
• Where are rods and cones located in the eye?

  • At the back of the retina
  • Rods are more numerous than cones

  
• How many times more rods are there than cones in the retina?

  About twenty times more

  
• What type of light do rods detect well?

  Low-intensity light levels
• What is a limitation of rods in terms of image detail?

  They contribute little detail to the image
• What do cones detect that rods do not?

  Different colors

  
• How many types of cones are there?

  Three types
• What does the graph show about rods' detection of light?

  Rods detect 100% of wavelengths from 380 to 650 nm

  
• How does the eye perceive white light?

  When all colors are not dispersed
• How does the brain process color signals from cones?

  By interpreting their weighted relative strengths
• What wavelengths do the three types of cones detect?

  Red, green, and blue
• What color appears dimmer to the eye?

  Blue light
• How can different colors be produced by the eye?

  • By combining different intensities of red, green, and blue light
  • Example: Yellow light from red and green cones
• Which cones does the brain use to detect purple light?

  Red and blue cones
• What will you not be asked to do in the exam regarding the eye?

  Draw images of eye parts
• What might you be asked to sketch in the exam?

  One of the graphs shown