Bukhovtsev-et-al-Problems-in-Elementary-Physics

PHYSICAL OPTICS 159
(for red light) with reference to the straight line connecting
the eye of the observer and the centre of the rainbow.
807. Explain from a qualitative point of view the appearance
of a double rainbow. How do the colours alternate in the primary
and the reflection rainbows?
808. Can a rainbow be observed at midday in Moscow during
the summer solstice (on June 22)?
Note. At this time the Sun is the highest above the horizon
in the northern hemisphere.
809. The length of a wave in water diminishes n times,
n being the refraction index. Does this mean that a diver cannot
see surrounding objects in their natural colours?
810. The word "excellent" is written on a sheet of white
paper with a red pencil and the word "good" with a green
pencil. A green and a red pieces of glass are available. Through
which glass can the word "excellent n
be seen?
811. Why do coated lenses (see Problem 782) have a purpleviolet
(lilac) tint?
812. Why do the colours of thin films (for example, oil films on
water) and the colours of a rainbow have different tints?
813. A thin soapy film is stretched over a vertical frame.
When the film is illuminated by white light it shows three
bands coloured purple (crimson), yellow and light-blue (bluegreen).
Find the arrangement and the order of the bands
814. Why does the Moon, purely white in the daytime, have
a yellowish hue after sunset?
815. Why does a column of smoke rising above the roofs of
houses seem blue against the dark background of the surrounding
objects, and yellow or even reddish against the background of
a bright sky?
816. Why do the colours of moist objects seem deeper and
richer than those of dry ones?