Physics Ch26-29

Identical rays of light in air are refracted upon entering three transparent materials: A, water, where the speed of light is 0.75c; B, ethyl alcohol (speed 0.7c; C, crown glass (speed 0.6c).

C,B,A

Does a single raindrop illuminated by sunlight deflect light of a single color or does it disperse a spectrum of colors? Does it do this by reflection, refraction, or both?

It disperses a spectrum of colors, by both reflection and refraction.

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.

shows a candle placed on the principal axis of a spherical concave mirror with the focal point F. One ray of light is shown leaving the center of the candle flame and reflecting off the mirror. This can be treated as _____________.

an incident ray passing through the focal point

The colors of ink used in CMYK printing are cyan, magenta, yellow, and _________.

black

When red, green, and blue light are absorbed, the result is _________.

black

Clouds are white due to _________.

scattering

What is its wavelength in Plexiglas, where light travels at 67%% of its speed in air?

λ = 400 nm

When you hold a spherical concave mirror with a 48.2-cm radius of curvature 39.5 cm in front of your face, you see an image of your face that is 61.8 cm in front of the mirror. What is the magnification of this image?

-1.56

What is the wavelength of a wave that has a frequency of 1 Hz and travels at 300,000 km/s?

300,000 km

When you hold a spherical concave mirror with a 48.2-cm radius of curvature in front of your face, you see an image of your face that is 61.8 cm in front of the mirror. What is the distance between the mirror and your face?

39.5 cm

How does a pigment affect light?

A pigment selectively absorbs some frequencies of light and transmits others.

Which of the following is a true statement about virtual images?

A virtual image is formed at the position from which the rays appear to have originated.

What produces an electromagnetic wave?

An oscillating or accelerating electric charge

Suppose we replace the lens in the video with one that has a longer focal length. To keep the image sharp, how should we move the screen?

Away from the lens

Wheels from a toy cart are rolled from a concrete sidewalk onto the following surfaces: A, a paved driveway; B, a grass lawn; C, close-cropped grass on a golf-course putting green. Due to slowing, each set of wheels bends at the boundary and is deflected from its initial straight-line course.

B,C,A

When something is painted red, what color is most absorbed?

Cyan

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.

What do electric and magnetic fields contain and transport?

Energy

Why are metals shiny?

Free electrons in metals vibrate when light strikes them, thereby reemitting the light as reflected light

What is the evidence for the statement that white light is a composite of all the colors of the spectrum?

In a rainbow, sunlight is spread into all the colors by passing through water drops.White light can be separated into all colors of the spectrum using a prism, and then these colors can be recombined to make white light.If you shine white light through a glass filter passing any spectral color, then that color will come through the filter.

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.

What happens to light when it falls upon a material that has a natural frequency equal to the frequency of the light?

It is absorbed.

If an object is placed a great distance away from and in front of a converging lens such as the one shown in the video, where will its image be formed?

It will be very near the focal point on the opposite side of the lens.

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.

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.

If you look with a magnifying glass at pictures printed in full color in this or other books or magazines, you'll notice three colors of ink plus black. What are these colors?

Magenta, cyan, and yellow

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.

Why is the sunset red?

Only the low-frequency red light penetrates the thick layers of atmosphere when the Sun is low in the sky.

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.

How does the frequency of a radio wave compare to the frequency of the vibrating electrons that produce it?

They are the same.

Why are red and cyan called complementary colors?

They can be added together to make white light.

Are eyeglasses made with "high index of refraction" materials thinner or thicker? Why?

Thinner. Light bends more entering high index of refraction materials.

In what region of the electromagnetic spectrum is the resonant frequency of electrons in glass?

Ultraviolet

What is the fate of the energy in ultraviolet light that is incident upon glass?

Ultraviolet light will be absorbed by the resonant vibration of electrons and turned into internal energy and a temperature increase.

Why do opaque materials become warmer when light shines on them?

Vibrations given by the light to their electrons, atoms, and molecules that absorb the light become internal energy, thus leading to a temperature increase.

What is the fate of the energy in visible light that is incident upon clear glass?

Visible light will be transmitted by the glass, losing little energy in the process, so the energy remains visible light energy.

What accounts for the whiteness of a cloud?

Water droplets of different sizes scatter a variety of light frequencies, resulting in a white cloud.

What happens to the wavelength and frequency of the light waves as they enter water from air?

Wavelength decreases, and frequency will stay the same.

When is the angle at which a ray of light strikes glass not the same as the angle it exits?

When the light strikes the glass in one medium (such as air) and exits the glass in another medium (such as water)

What is the resulting color if equal intensities of red light and cyan light are combined?

White

To what color of light are our eyes most sensitive?

Yellow-green

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.

Does the law of reflection hold for curved mirrors? Explain.

Yes. It is as if the curved mirror is made of many small plane mirrors at slightly different orientations to each other.

Specular reflection is common in the light reflected from _________.

a mirror

A certain radar installation tracks airplanes by transmitting electromagnetic radiation of wavelength 3.2 cm . Find the frequency of this radiation. Express your answer to two significant figures and include the appropriate units.

f =9.4 GHz

When white light is incident upon green glass the color that emerges is _________.

green

A sunset appears red in color due to _________.

higher frequencies of light scattered away

What kinds of molecules will scatter the low frequencies of light?

large molecules

The electromagnetic waves having the highest speed in free space are _________.

none in particular as gamma, radio, and light have the same speed

rank the image descriptions in the order that you would observe them if you were to move an object from very far away from a converging lens to very near it. The image is vanishingly small and very near the focal point. The image is infinitely large and infinitely far away. The image is real and inverted. The image is virtual and upright.

object far away The image is vanishingly small and very near the focal point. The image is real and inverted. The image is infinitely large and infinitely far away. The image is virtual and upright. object very near

Materials that do not transmit visible light are said to be _________.

opaque

What type or types of image can be displayed on a screen (for example, on a blank sheet of white paper)?

real

When a red rose is held in white light, the color of its petals appears _________.

red

Which of these colors of light represents the lowest visible frequency?

red

The sky is blue due mainly to atmospheric _________.

scattering

The wavelength of light changes as light goes from one medium to another, while the frequency remains the same. Is the wavelength longer or shorter in water than in air?

shorter

he bending is less because the light is already ___ in water, and slows only slightly more in your cornea. The index of refraction of your cornea is closer to that of ___ than of ___.

slowed down water air

What kinds of molecules scatter high frequencies of light?

small molecules

Find the time for a pulse of laser light to reach the Moon and to bounce back to Earth. Express your answer to two significant figures and include the appropriate units.

t = 2.5 s

If we were to receive a radio message from this star today, find the time when it would have been sent. Express your answer using two significant figures. The nearest star beyond the Sun is Alpha Centauri, 4.2×10^16m away.

t = 4.4 years ago

Find the time required for a pulse of radar waves to reach an airplane 5.2 km away and return.

t =3.5×10−5 s

What is meant by critical angle?

the minimum angle of incidence inside a medium where light is totally reflected

With all three lights are on, we insert an object that casts a shadow. What will be the colors of the shadows, and why?

the three shadows will be cyan, yellow, and magenta, because these are the complements of the three primary colors.

The smallest portion of the electromagnetic spectrum is _________.

visible light

When red, green, and blue light are combined, the result is _________.

white

Start with all three light sources on and no object to cast a shadow. If we turn off the blue source, what will the color be in the region that was originally illuminated by all three sources?

yellow

What is the color of the peak frequency of solar radiation when it is plotted versus wavelength?

yellow-green

A certain blue-green light has a wavelength of 600 nm (6×10−7×10−7 mm) in air. What is its wavelength in water, where light travels at 75%% of its speed in air?

λ = 450 nm

When you hold a spherical concave mirror with a 48.2-cm radius of curvature 19.4 cm in front of your face, you see an image of your face in the mirror. Where is this image located, with respect to the mirror?

99.5 cm behind the mirror

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.

hat happens to the speed of light waves when they enter water from air?

The speed decreases.

How is the wavelength of light related to its frequency?

The wavelength is inversely proportional to the frequency.

When white light strikes a prism, what happens and why?

The white light emerges with the colors separated, with the red light bending the least.

What are the principal differences between a radio wave and light? Between light and an X-ray?

Radio waves have a lower frequency and longer wavelength than visible light waves. Light waves have a lower frequency and longer wavelength than X-rays.

Why does a rainbow look like a curve when viewed from the ground?

Raindrops act like prisms that reflect the colors of light in particular angles depending on how the individual colors are bent by the prism. Light seen at that angle forms a bow shape.

The color of seawater is a result of the subtraction of what color?

Red

What color light is transmitted through a piece of red glass?

Red

What is the color of visible light of the lowest frequencies? Of the highest frequencies?

Red, violet

Cite the law of reflection.

The angle of incidence equals the angle of reflection.

When the flashlight is in the air and the refracted ray is in the water, what happens to the angle of refraction if you increase the angle of incidence?

The angle of refraction increases.

When the flashlight is in the water and the refracted ray is in the air, what happens to the angle of refraction if you increase the angle of incidence?

The angle of refraction increases.

When the flashlight is in the water and the refracted ray enters the air, how does the angle of refraction compare with the angle of incidence?

The angle of refraction is greater than the angle of incidence.

When the flashlight is in the air and the refracted ray enters the water, how does the angle of refraction compare with the angle of incidence?

The angle of refraction is smaller than the angle of incidence, other than when the flashlight is on the normal line.

How does the angle at which a ray of light strikes a pane of window glass compare with the angle at which it passes out the other side?

The angles are the same.

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.

When a car veers off the road such that the left front wheel goes off the pavement into the gravel before the right wheel, what will happen to the car, and why?

The car will tend to turn to the left. Because the left wheel hits the gravel first and slows down before the right wheel, the right wheel covers a greater distance, causing the car to turn to the left.

What is the effect on the color of a cloud when it contains an abundance of large droplets?

The cloud becomes dark.

What is the relationship between the direction of traveling rays of light and the line representing the wave crests?

The direction of the rays of light is perpendicular to the line representing the wave crests.

In the demonstration portion of the video, you were asked to think about the image of a candle formed by a concave mirror. Suppose that the lower half of the mirror were covered with black tape. How would that affect the image?

The entire image would remain but would become dimmer.

Relative to the distance of an object in front of a plane mirror, how far behind the mirror is the image?

The image is the same distance behind the plane mirror as the object is in front of it.

What is the relationship between index of refraction and the speed of light in a material?

The index of refraction is inversely proportional to the speed of light in a material.

The sound coming from one tuning fork can force another to vibrate. What is the analogous effect for light?

The light emitted by resonant vibrations of an electron around one atom can be absorbed by an electron with the same resonant frequency of vibration in another atom.

When the wheel of a cart rolls from a smooth sidewalk onto a plot of grass, the interaction of the wheel with the blades of grass slows the wheel. What slows light when it passes from air into glass or water?

The light oscillates electrons in the atoms of the glass or water. The electrons absorb some of the energy and reemit it after a delay at each atom.

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 is the sky blue when the Sun is overhead?

The molecules in the atmosphere scatter blue light more than any other light, so the sky looks blue.

What happens when light from the Sun interacts with the molecules of the atmosphere?

The molecules scatter the light.

Which of the following positions of an object will create a real image if the lens is a converging lens as shown in the video?

The object is very far from the lens.

What would the rainbow look like to a viewer in the sky, and why?

The rainbow would appear to be a complete circle, because Earth no longer obstructs our view when we are above.

What are the colors of the shadows cast by an object that is placed under blue and red lights only?

The red light casts a blue shadow and the blue light casts a red shadow, because the space not illuminated by red is illuminated by blue, and vice versa.