Week 10 - color vision

Question 1

Wavelength

Answer 1

Light has a wavelength, it is the distance from one peak to the next, different wavelengths correspond to different colours.

Question 2

Wavelength range in which we can normally see

Answer 2

400 nm to 700nm
But we can also see very powerful infrared lights and some people who have had their cataracts removed can see ultraviolet light

Question 3

Why did evolution give us eyes that see 400–700 nm?

Answer 3

The power in sunlight peaks there. Also, Earth’s atmosphere is
most transparent to these wavelengths.
And sea water, where eyes first evolved, is most transparent < 500
nm.

Question 4

3 types of cones

Answer 4

red (63%), green (31%) and blue (6%)

Question 5

What light do blue cones prefer

Answer 5

blue light

Question 5

What are we called because we sense three types of colour

Answer 5

trichromats

Question 5

What light do red and green cone pigments prefer

Answer 5

yellow and yellow-green light

Question 6

How does the brain infer colour

Answer 6

comparing data from 3 types of cones

Question 6

What light does rhodopsin prefer

Answer 6

blue-green light

Question 7

What light does melanopsin prefer

Answer 7

blue

Question 8

How do we produce ANY colour perception

Answer 8

by mixing three wavelengths

Question 9

what happens when red and green cones are hyperpolarizes but blue cones arent

Answer 9

percieve yellow light

Question 10

how can the brain be fooled when it comes to percieving colour?

Answer 10

A red and green light can produce the cone activities as a yellow light would and so we would still see yellow

Question 11

Spectral colours

Answer 11

Those that can be evoked by light of a single wavelength. They are the rainbow colors, from violet through blue,
green, yellow and orange to red.

Question 12

Extraspectral colours

Answer 12

colors such as purple or white are evoked only by a
mix of wavelengths, e.g. we see purple when 2 or more wavelengths
affect red and blue cones more than green cones.

Question 13

R + G cells

Answer 13

yellow channel
ganglion cells that are excited by red and green light

Question 14

R - G cells

Answer 14

red-green opponent channel
ganglion cells that are excited by red light but inhibited by green light

Question 15

G - R cells

Answer 15

ganglion cells that are excited by green light but inhibited by red light.

Question 16

B - R - G cells

Answer 16

ganglion cells that are excited by blue light but inhibited by red and green light
B-(R+G)

Question 17

what explains after images

Answer 17

opponent channels

Question 17

two types of blue - yellow opponents channel

Answer 17

B-(R+G)
(R+G)-B

Question 18

Daltonism

Answer 18

Red green color blindness

Question 19

How can a woman be a tetrachromat

Answer 19

If her 2 X-chromosomes code, say, 2 different functional “red” cone
pigments or any color

Question 19

inheritance pattern for red green color blindness

Answer 19

color blind fathers
have color-normal daughters who have color blind sons.
The genes for the red and green cones lie on the X chromosome. problems at these loci underlie 95%of all variations in color vision.

Question 19

reflectance

Answer 19

its tendency to reflect certain wave-
lengths of light and absorb others.
the reflectance of an object carries information about it

Question 20

color constancy

Answer 20

our brains can usually infer the reflectance, so we
see the ripe banana as yellow even in green light.

Question 21

how does the brain infer reflectance

Answer 21

comparing it to different part of the imge