Physics 2 exam 2

Suppose you stand in front of a spherical mirror (concave or convex). Is it possible for your image to be (a) real and upright (b) virtual and inverted?

(a) No. (b) No.

(a) Can the image formed by a concave mirror ever be projected directly onto a screen without the help of other mirrors or lenses? If so, specify where the object should be placed relative to the mirror. (b) Repeat part (a) assuming that the mirror is convex.

(a) Yes, if the distance between the object and the mirror is greater than the focal length of the mirror. (b) No, because the image is always behind the mirror.

(a) When you look at the back side of a shiny teaspoon held at arm's length, do you see yourself upright or upside down? (b) When you look at the other side of the spoon, do you see yourself upright or upside down? Assume in both cases that the distance between you and the spoon is greater than the focal length of the spoon.

(a) upright (b) upside down

The radius of curvature of a spherical convex mirror is 52 cm. What is its focal length?

-26 cm

When someone looks into a concave mirror from a distance of 25 cm, a virtual image is produced that is enlarged by a factor of 2. What is the image distance?

-50 cm

It is often thought that virtual images are somehow less important than real images. To show that this is not true, identify which of the following instruments normally produce final images that are virtual.

-a magnifying glass -eyeglasses -a compound microscope -an astronomical telescope

An object is placed in front of a spherical mirror, and the magnification of the system is m = -6. What does this number tell you about the image? (Select one or more of the following choices.)

-the image is larger than the object -the image is inverted relative to the object -the image is a real image

Makenzie walks directly toward a plane mirror at a speed of 0.30 m/s. Determine the speed of the image relative to her.

0.60 m/s

The speed of light in material A is 1.4 times as large as it is in material B. What is the ratio of the refractive indices, nA/nB, of these materials?

0.71

What is the speed of light in a vacuum?

299 792 458 m/s

An object is placed near two perpendicular plane mirrors as shown in the figure. How many images will be formed?

3

A concave mirror has a radius of curvature of 60.0 cm. How close to the mirror should an object be placed so that the rays travel parallel to each other after reflection?

30.0 cm

Light rays that are near and parallel to the principal axis of a concave mirror converge to a point 18 cm in front of the mirror. What is the radius of curvature of the mirror?

36 cm

A friend is standing 2 m in front of a plane mirror. You are standing 3 m directly behind your friend. What is the distance between you and the image of your friend?

7 m

Which of the following choices does not involve total internal reflection?

A fisherman observes a fish below the surface of the water at an apparent depth of 0.5 m.

A physics student desires to create a beam of light that consists of parallel rays. Which one of the following arrangements would allow her to accomplish this task?

A light bulb is placed at the focal point of a converging lens.

Which one of the following statements is true for a spherical mirror?

A mirror that is more curved has a smaller focal length than that for a less curved mirror.

Which one of the following statements concerning a virtual image produced by a mirror is true?

A virtual image is always upright relative to the object

What kind of image can a single converging lens not produce?

A virtual image that is upright and smaller with respect to the object.

Which one of the following statements concerning converging lenses is false?

An object cannot be placed in front of the lens such that a virtual image results.

An object is placed in front of a concave spherical mirror. Which of the following statements concerning the resulting image is false?

An object that is placed at a distance less than the focal length from the mirror will produce a real image.

An object is placed at the focal point of a converging lens of focal length f. What is the image distance?

At an infinite distance

An electromagnetic wave is traveling in a vacuum. The electric field E of the wave is doubled. What happens to the magnetic field B, the total energy density u, and the intensity S of the wave?

B doubles, u increases by a factor of four, S increases by a factor of four

In an old movie a photographic film negative is introduced as evidence in a trial. The negative shows an image of a house that no longer exists. The verdict depends on knowing exactly how far above the ground a window ledge was (the object height ho). The distance between the ground and the ledge on the negative (the image height hi) can be measured. What additional information is needed to calculate ho?

Both the object distance and the focal length are needed.

An electromagnetic wave travels in a vacuum. The wavelength of the wave is tripled. How is this accomplished?

By reducing the frequency of the wave by a factor of three.

Which one of the following statements best explains why chromatic aberration occurs in lenses, but not in mirrors?

Different colors of light are refracted by different amounts as the light passes through a lens.

Which one of the following expressions gives the correct relationship between the magnitudes of the electric and magnetic fields of an electromagnetic wave?

E=cB

Which one of the following statements concerning electromagnetic waves is false?

Electromagnetic waves are longitudinal waves.

Which one of the following choices is a statement of the principle of reversibility?

If the direction of a light ray is reversed, the light retraces its original path.

When an object is placed 15 cm from a lens, a virtual image is formed. Which one of the following conclusions is incorrect?

If the image is upright the lens must be a diverging lens.

Which one of the following statements is true concerning a magnifying glass?

It produces a virtual image

What type of single lens produces a virtual image that is inverted with respect to the object?

Neither a converging nor a diverging lens produces such an image.

Which one of the following statements concerning spherical mirrors is correct?

Only a concave mirror can produce an enlarged image, provided the object distance is less than the radius of curvature.

Which one of the following statements concerning rays is false?

Rays are parallel to the wave front.

Which statement regarding real and virtual images is correct?

Rays of light emanate from a real image, but only appear to do so from a virtual image.

In the discussion of the Doppler effect for electromagnetic waves, this effect differs from that of sound waves in which of the following ways?

The Doppler effect for electromagnetic waves is dependent on the relative speed of the source and observer.

When glasses use diverging lenses to correct for nearsightedness or converging lenses to correct for farsightedness, the eyes of the person wearing the glasses lie between the lenses and their focal points. When you look at the eyes of this person, they do not appear to have their normal size. Which one of the following describes what you see?

The converging lenses make the eyes appear larger, and the diverging lenses make the eyes appear smaller.

Which one of the following statements concerning an object and a single diverging lens is true?

The diverging lens always forms a virtual image of a real object.

Which one of the following statements concerning the energy carried by an electromagnetic wave is true?

The energy is carried equally by the electric and magnetic fields.

In a scene from a movie, a nearsighted character removes his eyeglasses and uses them to focus the nearly parallel rays of the sun to start a fire. What is physically wrong with this scene?

The eyeglasses have diverging lenses and cannot be used to focus parallel rays.

Which one of the following statements is true concerning the focal length of a lens?

The focal length is different for different colors because of dispersion.

A section of the surface of a hollow sphere has a radius of curvature of 0.60 m, and both the inside and outside surfaces have a mirror-like polish. What are the focal lengths of the inside and outside surfaces?

The focal length of the inside is +0.30 m and the focal length of the outside is -0.30 m.

A beam of light passes from air into water. Which is necessarily true?

The frequency is unchanged and the wavelength decreases.

For an object in front of a single convex mirror, what is the greatest distance behind the mirror at which the image can be found? (Image distances behind the mirror are negative.

The greatest image distance is equal to the focal length of the mirror.

Which one of the following statements concerning a convex mirror is true?

The image a convex mirror produces is closer to the mirror than it would be in a plane mirror for the same object distance.

An object is placed between the focal point and the center of curvature of a concave mirror. The object is then moved closer to the mirror, but still remains between the focal point and the center of curvature. Do the magnitudes of (a) the image distance and (b) the image height become larger or smaller?

The image distance and image height become larger.

Which one of the following statements is not a characteristic of a plane mirror?

The image is real

Which one of the following statements is not a characteristic of a plane mirror?

The image is real.

When an object is placed 25 cm from a lens, a real image is formed. Which one of the following conclusions is incorrect?

The image is upright.

Santa Claus looks at his reflection in a spherical Christmas tree ornament. Which one of the following statements concerning Santa's image is true?

The image must be smaller than Santa.

What causes chromatic aberration?

The index of refraction of the material from which the lens is made varies with wavelength

A ray of blue light travels through air and is refracted as it enters a glass prism shown in the figure. An unknown liquid is in contact with the right side of the prism. The light then follows the path shown. Which one of the following statements concerning this situation is true?

The index of refraction of the unknown liquid is the same as that of the glass.

The compound microscope discussed in Cutnell and Johnson's text is made from two lenses. Which one of the following statements is true concerning the operation of this microscope?

The lens closest to the object forms a real image; the other lens forms a virtual image.

A lens produces a virtual image that is upright relative to the object. What can one infer about this situation?

The magnification has a positive value.

Which one of the following statements is true concerning a mirror that has a negative focal length?

The mirror is convex.

Which one of the following statements is true concerning the radius of curvature of a concave mirror?

The radius of curvature for such a mirror is positive.

An object is situated to the left of a lens. A ray of light from the object is close to and parallel to the principal axis of the lens. The ray passes through the lens. Which one of the following statements is true?

The ray passes through a focal point of the lens only if the lens is a converging lens.

A ray of light leaves an object and passes through the focal point on the same side of a converging lens. The ray is then incident on the lens. Which one of the following statements correctly describes the subsequent path of the light after it leaves the lens?

The ray travels parallel to the principal axis.

The drawing shows an x, y, z coordinate system. A circular loop of wire lies in the z, x plane and, when used with an LC tuned circuit, detects an electromagnetic wave. Which of the following situations would result in the detection of an electromagnetic wave?

The wave travels along the z axis, and its electric field oscillates along the x axis.

Which one of the following statements relating to index of refraction n is false?

Values of n for solids and liquids indicate that the speed of light in these substances is greater than that in gases.

The indices of refraction for red, green, and violet light in glass are nred = 1.520, ngreen = 1.526, and nviolet = 1.538. When a ray of light passes through a transparent slab of glass, the emergent ray is parallel to the incident ray, but can be displaced relative to it unless the angle of incidence is zero. For light passing through a glass slab that is surrounded by air, which color is displaced the most?

Violet

Suppose you hold up a small convex mirror in front of your face. Which answer describes the image of your face?

Virtual, upright

Which one of the following statements concerning the image formed by a concave spherical mirror is true?

When the object distance is less than the focal length, the image is virtual.

Which one of the following statements concerning electromagnetic waves is false?

X-rays have longer wavelengths than radio waves.

Complete the following statement: The speed of light in a vacuum is

a constant value everywhere in the universe.

Approximately how long does it take for a radio wave to travel from the earth to the moon?

a second

Which one of the following will not generate electromagnetic waves or pulses?

a steady direct current

A real, single lens typically forms an image that is slightly out of focus. What is the general term for this phenomenon?

aberration

Parallel paraxial rays approach a converging lens. Where do the rays converge?

at the focal point

Complete the following sentence: The various colors of visible light differ in

both frequency and wavelength.

Complete the following statement: The energy carried by an electromagnetic wave is

carried by both the electric and magnetic fields.

What term is used to describe the maximum distance at which the fully relaxed eye can focus?

critical position

Complete the following statement: The term dispersion refers to the fact that the index of refraction of certain materials

depends on the wavelength of light.

Complete the following sentence: When electrons from a heated filament accelerate through vacuum toward a positive plate,

electromagnetic waves will be produced.

The table lists the index of refraction for various substances at 20 °C for light with a wavelength of 589 nm in a vacuum. Through which substance will light with a vacuum wavelength of 589 nm travel with the greatest speed?

ethyl alcohol

An object is placed at the focal point of a thin diverging lens of focal length f. What is the image distance?

f/2

Which of the following expressions applies to a convex spherical mirror of radius R?

f=-0.5R

When unpolarized light is incident on a sheet of polarizing material with a transmission axis oriented vertically, what percentage of the light is transmitted through the material?

fifty percent

A plane mirror is 6 ft tall. What is its focal length?

infinity

A ray of light originates in medium A and is incident upon medium B. For which one of the following pairs of indices of refraction for A and B is total internal reflection not possible

nA-1.28 nB-1.36

A coin is resting on the bottom of an empty container. The container is then filled to the brim three times, each time with a different liquid. An observer (in air) is directly above the coin and looks down at it. With liquid A in the container, the apparent depth of the coin is 7 cm, with liquid B it is 6 cm, and with liquid C it is 5 cm. Rank the indices of refraction of the liquids in descending order (largest first).

nC, nB, nA

What is the angle of refraction when the angle of incidence is equal to the critical angle?

ninety degrees

When vertically polarized light is incident on a sheet of polarizing material with a transmission axis oriented vertically, what percentage of the light is transmitted through the material?

one hundred percent

Sound waves are emitted from a pulsating point source and travel spherically outward from the source. What is the distance between two successive wave fronts?

one wavelength

A ray is __________

parallel to the velocity of the wave.

What term is used for the line that passes through the center of curvature of a spherical mirror and the mid-point of the mirror?

principal axis

An electromagnetic wave is traveling in a vacuum. The magnitudes of the electric and magnetic fields of the wave are _____________, and the electric and magnetic energies carried by the wave are _____________.

proportional (but not equal) to each other, equal

Which one of the following types of wave is fundamentally different than the other four?

sound waves

The bending of light as it moves from one medium to another with differing indices of refraction is due to a change in what property of the light?

speed

Complete the following statement: The polarization direction of an electromagnetic wave is determined by

the direction of the electric field component.

An object is placed at a known distance in front of a mirror whose focal length is also known. You apply the mirror equation and find that the image distance is a negative number. This result tells you that __________

the image is virtual.

Complete the following statement: When using two lenses in combination,

the image of the first lens becomes the object for the second lens.

When does dispersion occur?

the index of refraction varies with the wavelength of light

An object is situated at a known distance in front of a convex mirror whose focal length is also known. A friend of yours does a calculation that shows that the magnification is -2. After some thought, you conclude correctly that __________

the magnification should be +1/2

The most convincing evidence that electromagnetic waves are transverse waves is that

they can be polarized.

Complete the following statement: Fiber optics make use of

total internal reflection.

Which one of the following colors of visible light has the highest frequency?

violet

What is the correct order, beginning with shortest wavelength and extending to the longest wavelength, of the following colors in the visible light spectrum: blue, green, red, violet, and yellow?

violet, blue, green, yellow, red

Rays of light coming from the sun (a very distant object) are near and parallel to the principal axis of a concave mirror. After reflecting from the mirror, where will the rays cross each other at a single point? The rays __________

will cross at the focal point.

When horizontally polarized light is incident on a sheet of polarizing material with a transmission axis oriented vertically, what percentage of the light is transmitted through the material?

zero percent