Question 1

The ideal shape for the primary mirror of a telescope is
A) concave circular.
B) convex circular.
C) concave parabolic.
D) convex parabolic.
E) plane.

Accepted Answer

A concave parabolic mirror is the ideal shape for the primary mirror of a telescope because it can accurately focus parallel light rays to a single point, creating a clear and sharp image. The other options do not have the proper curvature needed for precise focusing of light.

Question 2

The variation of the speed of light in a transparent medium with frequency results in
A) interference.
B) diffraction.
C) dispersion.
D) diffuse reflection.
E) polarization.

Accepted Answer

The variation of the speed of light in a transparent medium with frequency causes the different colors of light to travel at different speeds, leading to the separation of light into its component colors. This phenomena is known as dispersion.

Question 3

In optics, what is meant by an "interface?"
A) optically connecting one computer to another
B) using the image created by one lens as the object for another lens
C) when the crest of one wave lines up with the trough of another wave
D) none of the above

Accepted Answer

An "interface" in optics refers to the boundary between two different media, where the direction of waves of light changes due to refraction or reflection, not to any of the options given.

Question 4

In this figure a light ray travels between air and glass. Which way did the light ray go? 
A) from the air into the glass
B) from the glass into the air
C) either A or B.
D) None of the above-this depicts an impossible situation.

Accepted Answer

The figure shows a light ray traveling from air into glass at point A, and then traveling from glass into air at point B. Therefore, the answer is either A or B, making choice C the correct answer. This situation is possible and follows the laws of refraction.

Question 5

An object is 50 cm in front of a plane mirror. Its image will be located
A) 50 cm in front of the mirror.
B) at the mirror's surface.
C) 50 cm behind the mirror.
D) 25 cm in front of the mirror.
E) 25 cm behind the mirror.

Accepted Answer

According to the laws of reflection, the image will be located the same distance behind the mirror as the object is in front of the mirror. Therefore, the image will be located 50 cm behind the mirror.

Question 6

A light ray bends when it goes from one medium to another because of
A) interference.
B) diffraction.
C) specular reflection.
D) refraction.
E) polarization.

Accepted Answer

Refraction is the bending of a wave when it enters a medium where its speed is different. This is due to the change in the wave's direction and speed as it passes from one medium to another.

Question 7

What is meant by the term "plane mirror?"
A) not an unusual mirror
B) a flat mirror
C) a horizontal mirror
D) none of the above

Accepted Answer

A plane mirror is a flat mirror that reflects light and forms an image that is virtual, upright, and of the same size as the object being reflected.

Question 8

Upon entering a medium in which the speed of light is 1.5 × 10⁸ m/s from a medium in which the speed of light is 2 × 10⁸ m/s, an oblique light ray will be _____________ the normal to the interface between the two media. A) bent away from B) bent toward C) travel along D) remain undeviated with respect to

Accepted Answer

When light enters a medium where its speed decreases (from 2 × 10^8 m/s to 1.5 × 10^8 m/s in this case), it bends toward the normal according to Snell's Law. This is because the angle of incidence in the faster medium is larger than the angle of refraction in the slower medium.

Question 9

In air a light source emits a wavelength of 630 nm. Under water the wavelength of this light will be
A) 630 nm.
B) less than 630 nm.
C) more than 630 nm.
D) unpredictable.

Accepted Answer

The refractive index of water is 1.33, which means that light travels slower in water than in air. According to the equation λ = c/f, where λ is wavelength, c is the speed of light and f is frequency, the wavelength decreases as the speed of light decreases. Therefore, under water, the wavelength of the light will be less than 630 nm.

Question 10

What makes pink ink pink?
A) refraction
B) selective absorption
C) dispersion
D) none of the above

Accepted Answer

Pink ink appears pink due to selective absorption of certain wavelengths of light. The ink absorbs most of the colors in the visible spectrum, but reflects back primarily red and blue wavelengths, which combine to give the appearance of pink.

Question 11

The type of mirror that will allow you to see large areas normally hidden from your view is
A) concave.
B) convex.
C) plane.
D) half-silvered.
E) Polaroid.

Accepted Answer

A convex mirror is designed to diverge light and create a wider field of view. This makes it ideal for seeing larger areas that would be hidden from view with a plane or concave mirror. A half-silvered mirror and Polaroid filters are not designed for this purpose.

Question 12

A one-way mirror works because of
A) interference.
B) diffraction.
C) its surfaces being half-silvered.
D) dispersion.
E) polarization.

Accepted Answer

A one-way mirror is made by coating one side of a piece of glass with a thin layer of metal, usually silver. This coating is called a half-silvered surface because it reflects about half of the light that strikes it and allows the other half to pass through. This creates an effect where one side of the mirror appears reflective while the other side appears transparent, allowing people on one side to see through it while people on the other side cannot. This effect is often used in surveillance rooms or police stations for one-way viewing.

Question 13

New telescopes are using "adaptive optics."  What is that?
A) using parabolic instead of spherical mirrors
B) using computer image processing to enhance images
C) building mirrors in hexagonal segments
D) continually adjusting the mirror's shape during observations

Accepted Answer

Adaptive optics is the technology of adjusting the shape of a telescope's mirror, in real-time, to correct for atmospheric distortions. This is done by measuring the distortion of incoming light waves and using computer-controlled actuators to alter the shape of the mirror, allowing for clearer and sharper observations.

Question 14

The sky is blue because of
A) interference.
B) diffraction.
C) scattering.
D) dispersion.
E) polarization.

Accepted Answer

The sky appears blue because of scattering, specifically Rayleigh scattering. As light from the sun enters Earth's atmosphere, it encounters gas molecules and other particles which scatter the light in all directions. Shorter wavelengths (blue and violet) are scattered more easily than longer wavelengths (red and orange), which is why the sky appears blue during the daytime.

Question 15

Parallel light rays from a distant object strike the surface of a concave mirror. After reflecting from the mirror's surface, the rays will converge at
A) the mirror's focal point.
B) a point beyond the mirror's focal point.
C) a point nearer than the mirror's focal point.
D) none of the above.

Accepted Answer

A concave mirror is converging in nature, meaning it brings parallel rays of light together to a single point. This point is known as the focal point, which is located half the distance between the mirror's surface and its center of curvature. Therefore, parallel rays from a distant object will converge at the mirror's focal point after reflecting from the surface of a concave mirror.

Question 16

Diverging light rays from a nearby object (a few focal lengths away from the mirror) strike the surface of a concave mirror. After reflecting from the mirror's surface, the rays will converge at
A) the mirror's focal point.
B) a point beyond the mirror's focal point.
C) a point nearer than the mirror's focal point.
D) none of the above.

Accepted Answer

When light rays diverge from a nearby object and reflect from the surface of a concave mirror, they will converge to a single point beyond the mirror's focal point. This is because a concave mirror is curved inward, which causes light rays to pass through a converging path after reflecting from its surface.

Question 17

When you look into a pool of water, the depth looks less than it actually is because of
A) interference.
B) diffraction.
C) specular reflection.
D) refraction.
E) polarization.

Accepted Answer

When light waves pass from one medium (in this case, air) to another medium (water), their speed and direction change, resulting in the phenomenon of refraction. This causes the light rays to bend as they enter and exit the water, making the depth appear shallower than it actually is.

Question 18

Rank the following media in order according to the speed of light in them, from slowest to fastest: vacuum, air, water and glass.
A) air, water, glass, vacuum
B) glass, air, water, vacuum
C) water, glass, air, vacuum
D) glass, water, air, vacuum
E) none of the above

Accepted Answer

The speed of light in a medium depends on the refractive index of the medium. The refractive index of a medium is a measure of how much the speed of light is reduced when it enters the medium. The higher the refractive index, the slower the speed of light in that medium.

Vacuum has the highest possible speed of light - it travels at approximately 299,792,458 meters per second.

Glass has the slowest speed of light among the given options due to its high refractive index. The refractive index of glass varies depending on the type of glass, but it typically ranges from around 1.4 to 1.7.

Water has a refractive index of around 1.33, which is lower than glass but still higher than air.

Air has the lowest refractive index among the given options, so it has the fastest speed of light among these four media.

Therefore, the correct order from slowest to fastest speed of light is glass, water, air, vacuum, which is choice D.

Question 19

The primary mirror in an astronomical telescope must be a
A) half-silvered mirror.
B) convex mirror.
C) concave mirror.
D) plane mirror.

Accepted Answer

The primary mirror in an astronomical telescope must be a concave mirror, which is used to collect and focus light from distant objects.

Question 20

You see colors with a prism because of
A) interference.
B) diffraction.
C) specular reflection.
D) dispersion.
E) polarization.

Accepted Answer

Dispersion is the process of separating light into its constituent colors or wavelengths. This occurs because different colors of light have different wavelengths and bend at slightly different angles when passing through a prism, producing the rainbow of colors we see.

Quiz 9: Optics

The ideal shape for the primary mirror of a telescope is

The variation of the speed of light in a transparent medium with frequency results in

In optics, what is meant by an "interface?"

In this figure a light ray travels between air and glass. Which way did the light ray go?

An object is 50 cm in front of a plane mirror. Its image will be located

A light ray bends when it goes from one medium to another because of

What is meant by the term "plane mirror?"

Upon entering a medium in which the speed of light is 1.5 × 108 m/s from a medium in which the speed of light is 2 × 108 m/s, an oblique light ray will be _____________ the normal to the interface between the two media.

In air a light source emits a wavelength of 630 nm. Under water the wavelength of this light will be

What makes pink ink pink?

The type of mirror that will allow you to see large areas normally hidden from your view is

A one-way mirror works because of

New telescopes are using "adaptive optics." What is that?

The sky is blue because of

Parallel light rays from a distant object strike the surface of a concave mirror. After reflecting from the mirror's surface, the rays will converge at

Diverging light rays from a nearby object (a few focal lengths away from the mirror) strike the surface of a concave mirror. After reflecting from the mirror's surface, the rays will converge at

When you look into a pool of water, the depth looks less than it actually is because of

Rank the following media in order according to the speed of light in them, from slowest to fastest: vacuum, air, water and glass.

The primary mirror in an astronomical telescope must be a

You see colors with a prism because of

Upon entering a medium in which the speed of light is 1.5 × 10⁸ m/s from a medium in which the speed of light is 2 × 10⁸ m/s, an oblique light ray will be _____________ the normal to the interface between the two media.