SCIENCE 8 – RODS & CONES WORKSHEET NAME: 1) Why are rod cells more useful for night vision? 2) Why are cone cells more useful for colour vision? 3) Why is it necessary to have three kinds of cone cells operating in order to have full colour vision? 4) Most mammals, including dogs and cats, cannot see colours. How would the retina of a cat’s eye be different from the retina of a human eye? 5) Place the letters of the following descriptions into the appropriate circle: a. About 100 million e. Evenly distributed i. About 6 million m. Night vision b. Used in bright light f. Absorbs all wavelengths j. 3 types n. Mostly found in centre of retina c. 1 type g. Fast response to light k. Lots of pigment o. Slow response to light d. Very little pigment h. Day vision l. Used in low light p. Absorbs 1 of 3 different wavelengths rod cone Use the following graph to answer questions 3 to 5 Use the visible spectrum on page 6 of your notes to answer question 6 (b) and 7 (b). 6) Consider the line labelled “R”, for red-sensitive cone cells. (a) At what wavelength, in nanometres, are these cells most effective at detecting light? (b) What colour does the wavelength in (a) correspond to? (c) Which colour are the red-sensitive cells able to detect more easily – green or red? (d) Suggest a reason why these cells are called red-sensitive cells even though they detect many other colours as well. 7) Consider the line labelled “BW”, for black- and white-sensitive rod cells. (a) At what wavelength do the black- and white-sensitive rod cells absorb light most efficiently? (b) What colour does the wavelength (a) correspond to? 8) Examine the graph and explain why humans are able to detect faint amounts of green light.