Textbook
Chapter 9, page 287: P1, P2, P3 and Chapter 10, page 302: P1
P1. (a) A Venusian can detect light from 200 nm
to 350 nm and from 400 nm to 500 nm.
(b) A Venusian can detect light from
200 nm to 350 nm. Humans cannot see these colors – they are too blue
(c) A human can detect light from 350 nm to 400 nm and from 500 nm to 650 nm.
Venusians cannot see these colors
(d) The maximum sensitivity is at about 275 nm. This
color excites two cones about equally, and the sum of the these two excitations
is probably greater than the peak values of any one excitation acting by
itself.
(e) A wavelength of 275 nm would be a spectral
complement for any wavelength between 400 and 500, since that pair of
wavelengths would excite all 3 cones.
(f) 275 nm would be the spectral complement for both
425 and 450. In both cases, either pair of wavelengths would excite all 3 cones
and could produce a “white” response.
Although it is not part of the question, note that
wavelengths between 200 nm – 250 nm and between 300 nm – 350 nm have no
complements. These wavelengths excite only one cone, and there is no other
single wavelength that could excite the other two cones to produce a “white”
response.
P2. (a) There are no wavelengths that a Martian
can see that a human cannot.
(b) Humans can see many wavelengths
that martians cannot. For example, bands near 500 nm, near 600 nm, and below
450 nm.
(c) Martians have no spectral
complements. There are no two colors that can excite all three cones.
P3. The Martian can see the light on the TV program because the
street light shown on the television picture is implemented using a combination
of the 3 primary colors, and the Martian can see 650 nm red. However, the
Martian cannot see the real street light because it is a monochromatic 589 nm,
and the Martian cannot see that wavelength.
Ch. 10, P1.
(a) 3 colors are used because that number is the same as
the number of primaries in the human eye, so that color pictures look like the
real thing. Using fewer colors would result in some hues not being displayed
properly and using more colors would not provide any benefit in most cases.
(note that this is not completely true. Color photography suffers from the
usual problem with saturated colors.)
(b) Most color films record the subtractive primaries:
cyan, yellow and magenta. Some older positive films recorded the additive
primaries: red, green and blue
(c) No. subtractive films use cyan, yellow and magenta
while additive films use red, green and blue.