Question

The photoreceptors in the human eye, called rods and cones, have different sensitivities to different wavelengths of electromagnetic waves. (Figure 1) (Notice that the y axis in the figure is a logarithmic scale.) The rods, which number over 100 million, can only be activated by a certain range of wavelengths, but they do not pass any color information to the brain. In other words, they note differences in shades of grey (from black to white) and are responsible for a person's ability to see in dim light. Cones, which number around 6 million, give us color vision. Cones come in three different kinds: 64% of cones are sensitive to long wavelengths of visible light (toward the red end of the spectrum), 32% are sensitive to medium wavelengths, and the remaining 2% are sensitive to short wavelengths (toward the blue end of the spectrum). Colors are differentiated on the basis of the extent to which visible light stimulates each kind of cone.

1.Do rods have their peak sensitivity at a higher or lower frequency than cones?

a) Higher

b)Lower

2.Do rods and cones have similar sensitivities near the red or near the violet edge of the visible spectrum?

a)red

b)violet

3.Is it easier to detect a dim red source or a dim violet source of light?

a)red

b)violet

4.At 500 nm, which of the following statements is true?

a)Rods are about 1000 times more sensitive than cones.

b)Rods are about 3 times more sensitive than cones.

c)Rods and cones are about equally sensitive.

d)Cones are about 3 times more sensitive than rods.

e)Cones are about 1000 times more sensitive than rods.

Answer 1

(1) higher

(2) red

(3) violet

(4)Rods are about 1000 times more sensitive than cones