HW 1

In the demonstrations we used a laser pointer and chalk dust to show that light travels in a straight line.

We use different models to explain our observations about light. The observation of light traveling in straight lines is most easily explained with the ray model.

The visible spectrum can be crudely broken into three roughly equal parts characterized as the primary colors of light. They are red, blue, and green.

When red light and green light are added together in roughly equal intensities, the result is yellow.

When yellow light and blue light are added together in roughly equal intensities, the result is white light.

When red light and white light are added together in roughly equal intensities, the result is pink light.

An opaque disk blocks light from a point source and makes a shadow on a wall. If the disk is aligned perpendicular to the path of the light and placed half-way between the light source and the wall, the diameter of its shadow is twice the diameter of the disk.For the situation of the preceding problem, the distance between the light source and wall is kept constant. If the disk is moved closer to the source, the diameter of the disk's shadow increases.

An opaque disk blocks light from a point source and makes a shadow on a screen. The disk is aligned perpendicular to the path of the light and placed midway between the light source and the screen. If the positions of the screen and the disk are constant and the source is moved closer to the disk, the diameter of the shadow gets fuzzier.

What is an umbra? Umbra is complete (darkest) shade.

Which of the following sources will give the sharpest shadow of an object placed between the source and a screen? A point source.

HW 2

What is the frequency of red light that has a wavelength of 600 nanometers in free space (the vacuum)? (Hint: 1 nanometer = 10-9 m.) 5 x 1014 Hz

The range of wavelengths of visible spectrum is 400 - 700 nm.

A local radio station operates on a frequency of 97.50 MHz. What is the wavelength of its radio waves? Give your answer in meters. 3.08 m

The speed of light is 3.0 x 108 m/s.

A physical phenomena that occurs at one place at one time and a distant places at later times that are proportional to the distances is known as a wave.

The distance from the sun to the earth is 1.5 x 1011 m. How long does it take for light to travel from the sun to the earth? 500 s

Light is a transverse electromagnetic wave.

What is the speed of light in glass that has an index of 1.5? 2/3 c

What is the index of refraction of clear acrylic plastic in which light travels at a speed of 1.95 x 108 m/s? 1.54

The index of refraction n is defined to be c/v, where c is the speed of light in vacuum and v is the speed of light in matter.

The speed of light in water is 3/4 the speed of light in vacuum. What is the index of refraction of water? 4/3

HW 3

The angle of incidence is the angle measured between the direction of the incident ray and the normal to the surface.

The statement that the angle of reflection equals the angle of incidence is known as the law of reflection.

When a wave (such as a light wave) encounters a sudden change of medium, as in going from air to glass, in general the wave is partially reflected and partially transmitted.

The plane of incidence is the plane that contains the incident ray and the reflected ray.

In describing reflection, the normal always lies in the plane of incidence.

Your image in a plane mirror is erect and virtual.

Suppose you are standing 3 feet from a plane mirror and facing it. If you walk closer to the mirror, your image moves toward you and stays the same size.

Suppose you take a pencil and put its point in the contact with a mirror. If the reflected pencil point does not contact the real pencil point you have a back surface mirror.

Which of the following is not true for a convex mirror? The image of a real object may be virtual or real depending on the object distance.

Which of the following is true for a concave mirror? The image of a real object may be virtual or real depending on the object distance.

A wide angle mirror in a grocery store is made from a section of a sphere whose radius of curvature is 1.5 m. The image of the person standing 1.5 meters in front of the mirror is erect, virtual, and smaller than the person.

An object is placed between the radius of curvature and the focal length of a concave spherical mirror. The resulting image is real, inverted, and larger than the object.

An object is located in front of a convex spherical mirror. As the object moves closer to the mirror its image gets bigger.

HW 4

When a beam of light traveling in air enters a glass prism with index of refraction of 1.52, which of the following quantities remains the same? The frequency of the wave is the same.

When light incident on a surface with angle of incidence passes from a medium of lower index of refraction into one with a higher index, the light ray bends toward the normal to the surface.

When light incident on a surface with angle of incidence passes from a medium of higher index of refraction into one with a lower index, the light ray bends away from the normal to the surface.

The expression known as Snells Law gives the relationship between the angle of incidence and the angle of refraction.

Light incident in air on a triangular glass prism is always bent toward the base of the prism.

When light goes from a medium of higher index to lower index there is a limiting angle of incidence beyond which the light is totally reflected.

When light goes from a medium of higher index to lower index there is a limiting angle of incidence known as the critical angle.

A dime is viewed through a positive lens (focal length of + 4.0 cm). The dime is 2 cm from the lens as seen in the figure below. Where is the image of the dime? (Hint: A positive image distance is to the right of the lens and a negative image distance is to the left of the lens.) -4 cm

To the observer on the right, the dime in the previous problem appears larger.

If the dime in the previous problem is moved closer to the lens, its image becomes smaller.

A dime is viewed through a negative lens (focal length of -4.0 cm). The dime is 4 cm from the lens as seen in the figure above. Where is the image of the dime? (Hint: A positive image distance is to the right of the lens; a negative image distance is to the left of the lens.)-2 cm

To the observer on the right, the dime in the previous problem appears smaller.

If the dime in the previous problem is moved closer to the lens, its image becomes larger.

A lens is called a positive lens if it is a converging lens.

Which of the following is not true for a diverging lens? The image of a real object may be virtual or real depending on the object distance.

HW 5

The near point of the "normal" eye is 25 cm.

Changes in the eye as it adjust to different levels of brightness is called adaptation.

Someone who requires glasses with diverging lenses for vision is known as myopic.

A person with a near point of 65 cm is considered hyperopic.

Someone with a near point of 1.0 m and no accommodation problems has vision that is described as hyperopic.

What is the strength (in diopters) of a converging lens with a focal length of 200 cm? 0.5

What is the strength (in diopters) of a diverging lens with a focal length of -200 cm? 0.5

Changing the shape of the eye lens to focus at different distances is called accommodation.

A binocular is rated as 7 x 35. It has a magnification of 7x.

A simple magnifier consists of a single positive lens with a focal length of 4 cm. What is the approximate magnifying power of this lens? 6x

An astronomical telescope has a 30-cm-focal-length objective and an eyepiece with a focal length of + 5.0 cm. The magnification of the telescope is 6x.

The image seen with the astronomical telescope of the previous problem is inverted.

HW 6

Which of the following is not one of the six psychological cues for depth? Stereopsis

A stereo pair of images printed one on top of the other in contrasting colors that can be blocked by corresponding color filters in known as a/an analglyph.

Which of the following is one of the six psychological cues for depth? Aerial perspective

The separation of viewpoints of a stereopair of images is known as binocular disparity.

Consider a stereopair of images with a left-eye view and a right-eye view. What happens if you view it so that the left eye sees the right-eye view and the right eye sees the left-eye view? The depth will be inverted giving a pseudoscopic image.

The loss of color and sharpness with distance due to the scattering of light by the air is called aerial perspective.

The critical flicker fusion frequency is 50 Hz.

Edge enhancement is a result of lateral inhibition.

The effect that objects maintain their lightness independently of the brightness is known as lightness constancy.

In the Craik-O'Brien illusion two regions of gradually changing shades of gray meet abruptly so that their junction is clearly visible. When the junction region is covered, perhaps with a pencil, the two regions then appear to be the same uniform shade of gray. This experiment tells us that our visual system is insensitive to gradual changes but very sensitive to abrupt changes in intensity.

The physical quantity that we measure with a light meter is called brightness.

The effect in which the lightness of a particular area is influenced by the lightness of surrounding regions is known as simultaneous lightness contrast.

The overall illumination (measured with a light meter) is known as brightness.