What is the color of visible light of the lowest frequencies? Of the highest frequencies?
Red, Violet
How is the fact that an electromagnetic wave in space never slows down consistent with the law of conservation of energy?
If light slowed down, its energy would decrease, thereby violating the law of conservation of energy.
How does the frequency of a radio wave compare to the frequency of the vibrating electrons that produce it?
They are the same.
What is the wavelength of a wave that has a frequency of 1 Hz and travels at 300,000 km/s?
300,000 km
What does a changing electric field induce?
A changing magnetic field
About how much of the measured electromagnetic spectrum does light occupy?
Less than 1 millionth of 1%
What does a changing magnetic field induce?
A changing electric field
What happens to light when it falls upon a material that has a natural frequency above or below the frequency of the light?
It is reemitted.
Which warms more quickly in sunlight - a colorless or a colored piece of glass? Why?
A colored piece of glass warms quickest because it absorbs more frequencies of light, thus converting the energy to temperature.
How do the rods in the eye differ from the cones?
The rods are rod-shaped and are more sensitive to dim light. The cones are cone-shaped and are color-sensitive.
How does a pigment affect light?
A pigment selectively absorbs some frequencies of light and transmits others.
How does the average speed of light in glass compare with its speed in a vacuum?
The average speed of light in glass is about 67% of the speed of light in a vacuum.
How does the speed of light that emerges from a pane of glass compare with the speed of light incident on the glass?
They are the same.
Distinguish between an umbra and a penumbra.
No light from the source enters the shadow in an umbra, while some, but not all, light from the source enters the penumbra.
What occurs when the outer electrons that buzz about the atomic nucleus encounter electromagnetic waves?
They are forced into vibration, absorbing or emitting electromagnetic waves.
Why do wet objects normally look darker than the same objects when dry?
Light bounces around inside the transparent water region covering a wet object, getting absorbed more on each bounce.
What is the fate of the energy in infrared light incident on glass?
Infrared light will make atoms vibrate, thus becoming internal energy and a temperature increase.
In what region of the electromagnetic spectrum is the resonant frequency of electrons in glass?
Ultraviolet
Do Earth and the Moon always cast shadows? What do we call the occurrence where one passes within the shadow of the other?
Yes, they both cast shadows. When one passes into the shadow of the other, there is an eclipse.
To what color of light are our eyes most sensitive?
Yellow-Green
What is the effect on the color of a cloud when it contains an abundance of large droplets?
The cloud becomes dark.
What frequency ranges of the radiation curve do red, green, and blue light occupy?
Red: low; green: middle; blue: high frequencies
What color results when red is subtracted from white light?
Cyan
Why does the sky sometimes appear whitish?
Large particles in the atmosphere scatter longer wavelength light that adds to the blue light to create white light.
What is the resulting color if equal intensities of red light and cyan light are combined?
White
What part of the visible electromagnetic spectrum is most absorbed by water?
Red
Why does water appear cyan?
Water absorbs red light. White minus red is cyan.
Why does the Sun look reddish at sunrise and sunset but not at noon?
The longer path length of sunlight at sunrise and sunset scatters out more blue light.
Why does the sky normally appear blue?
Air molecules have resonances in the ultraviolet, so they scatter blue light more than red light.
What are the subtractive primary colors?
Magenta, cyan, and yellow
When something is painted red, what color is most absorbed?
Cyan
What accounts for the whiteness of a cloud?
Water droplets of different sizes scatter a variety of light frequencies, resulting in a white cloud.
Why does the color of sunsets vary from day to day?
Different particles in the air each day scatter and absorb different wavelengths of light, thus giving the sky many different colors.
Why are red, green, and blue called the additive primary colors?
Adding appropriate amounts of red plus green plus blue lights can produce almost any color of the spectrum.
Red+Green+Blue
White
When red, green, and blue light are absorbed, the result is
Black
The sky is blue due mainly to atmospheric
Scattering
A sunset appears red in color due to
higher frequencies of light scattered away
Clouds are white due to
Scattering
The color of seawater is a result of the subtraction of what color?
Red