Phys 23,24,25 Homework and Pre-lecture

Suppose you are standing about 3 m in front of a mirror. You can see yourself just from the top of your head to your waist, where the bottom of the mirror cuts off the rest of your image. If you walk one step closer to the mirror

you will not be able to see any more of your image.

You want to create a spotlight that will shine a bright beam of light with all of the light rays parallel to each other. You have a large concave spherical mirror and a small lightbulb. Where should you place the lightbulb?

At the focal point of the mirror.

A ray of light passes from air into a block of clear plastic. How does the angle of incidence in the air compare to the angle of refraction in the plastic?

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

Which of the following statements are true concerning compound microscopes?

In a compound microscope, the final image is a virtual image. In a compound microscope, the image formed by the objective lens is a real image.

While you are photographing a dog, it begins to move away. What must you do to keep it in focus?

Move the lens closer to the sensor or film.

If a thin film has a thickness that is

None of the above is always true

A convex lens is placed on a flat glass plate and illuminated from above with monochromatic red light. When viewed from above, concentric bands of red and dark are observed. What does one observe at the exact center of the lens where the lens and the glass plate are in direct contact?

One observes a dark spot.

When you look at a fish in a still stream from the bank, the fish appears shallower than it really is due to refraction. From directly above, it appears

Shallower than its real depth

A single-slit diffraction pattern is formed on a distant screen. If the width of the single slit through which light passes is reduced, what happens to the width of the central bright fringe? Assume the angles involved remain small.

The central bright fringe becomes wider.

A double-slit diffraction pattern is formed on a distant screen. If the separation between the slits decreases, what happens to the distance between interference fringes? Assume the angles involved remain small.

The distance between interference fringes increases.

Which of the following statements are true concerning the eye?

The far point of the normal eye is infinity. Astigmatism refers to a defect in which the surface of the cornea is not spherical. Instead, it is more sharply curved in one plane than another. Nearsightedness can be corrected with a diverging lens

A ray of light crosses a boundary between two transparent materials. The medium the ray enters has a larger optical density. Which of the following statements are true?

The frequency of the light remains constant as it transitions between materials. The wavelength of the light decreases as it enters into the medium with the greater optical density.

Consider two diffraction gratings with the same slit separation. The only difference between the two gratings is that one grating has 5 slits and the other 10 slits. Both gratings are illuminated with a beam of the same monochromatic light. Which of the following statements are true?

The grating with 10 slits produces better-defined (narrower) peaks. Both gratings produce the same separation between peaks.

Consider two diffraction gratings. One grating has 3000 lines per cm, and the other one has 6000 lines per cm. Both gratings are illuminated with a beam of the same monochromatic light. Which grating produces the greater dispersion?

The grating with 6000 lines produces the greater dispersion.

Which of the following statements are true for an image formed by a plane mirror?

The image formed by a plane mirror is always an upright image. The image formed by a plane mirror is always a virtual image. The image always appears to be located the same distance behind the mirror as the object is located in front of the mirror.

When glasses (or contact lenses) are used to correct nearsightedness, where should the corrective lens form an image of an object located at infinity in order for the eye to form a clear image of that object?

The lens should form the image at the far point.

When glasses (or contact lenses) are used to correct farsightedness, where should the corrective lens form an image of an object located between the eye and the near point in order for the eye to form a clear image of that object?

The lens should form the image at the near point.

In a double-slit experiment, two beams of coherent light traveling different paths arrive on a screen some distance away. What is the path difference between the two waves corresponding to the third bright band out from the central bright band?

The path difference between the two waves is three wavelengths.

Two beams of coherent light travel different paths, arriving at point P. If the maximum destructive interference is to occur at point P, what should be the path difference between the two waves?

The path difference between the two waves should be one-half of a wavelength.

A beam of light, which is traveling in air, is reflected by a glass surface. Does the reflected beam experience a phase change, and if so, by how much is the phase of the beam changed?

The reflected beam experiences a 180° phase change.

Which of the following statements are true concerning the reflection of light?

The reflection of light from a rough surface is called diffuse reflection. The reflection of light from a smooth surface is called specular reflection.

A soap film is viewed in white light. If the film is much thinner than the wavelength of blue light, what is the appearance of the film?

The soap film appears totally transparent because it reflects no visible light.

A single-slit diffraction pattern is formed on a distant screen. If the distance from the slit to the screen is doubled, by what factor will the width of the central bright fringe on the screen change? Assume the angles involved remain small.

The width of the central bright fringe will be twice its original size.

A double-slit experiment yields an interference pattern due to the path length difference from light traveling through one slit versus the other. Why does a single slit show a diffraction pattern?

There is a path length difference from waves originating at different parts of the slit.

When the reflection of an object is seen in a flat mirror, the image is

Virtual and upright

Which of the following statements are true concerning sign conventions for image formation?

When the object is on the same side of the reflecting or refracting surface as the incoming light, the object distance is positive; otherwise, it is negative. For an upright image, the magnification is positive; for an inverted image, the magnification is negative. When the center of curvature of a spherical mirror is on the same side as the reflected light, the radius of curvature is positive; otherwise, it is negative.

Which of the following statements are true for images formed by spherical mirrors?

A convex mirror always produces a virtual image of an object placed in front of it A convex mirror always produces an upright image of an object placed in front of it.

Which of the following statements are true for images formed by thin lenses?

A diverging lens always produces a virtual image of an object placed in front of it. A diverging lens always produces an upright image of an object placed in front of it.

At Point A is the interference between the two sources constructive or destructive? At point B,C,D?

A: Constructive B: Destructive C: Destructive D: Constructive

The colors in a rainbow are caused by

different amounts of refraction for light of different colors by the water in the raindrops.

As the object moves from just outside the focal point of a converging lens to just inside it, the image goes from _________ to ____________.

large and inverted to large and upright

Suppose a ray of light traveling in a material with an index of refraction na reaches an interface with a material having an index of refraction nb. Which of the following statements must be true for total internal reflection to occur?

na > nb The angle of incidence must be greater than the critical angle.

If the distance from your eye's lens to the retina is shorter than for a normal eye, you will struggle to see objects that are

nearby

Virtual images can be formed by

plane and curved mirrors, and lenses.

Light passing through a double-slit arrangement is viewed on a distant screen. The interference pattern observed on the screen would have the widest spaced fringes for the case of

red light and a small slit spacing.

How do eyeglasses help a nearsighted person see more clearly?

Diverging lenses bend light entering the eye, so the image focuses farther from the front of the eye.