Q&A Hero

Q: When we breathe we inhale oxygen, , and exhale carbon dioxide, , plus water vapor, O. Which likely has more mass, the air that we inhale or the same volume of air we exhale? Does breathing cause you to lose or gain weight? A) The air we inhale has more mass; Breathing causes you to lose weight. B) The air we exhale has more mass; Breathing causes you to lose weight. C) The air we inhale has more mass; Breathing causes you to gain weight. D) The air we exhale has more mass; Breathing causes you to gain weight.

Q: The isotope lithium-7 has a mass of 7.0160 atomic mass units, and the isotope lithium-6 has a mass of 6.0151 atomic mass units. Given the information that 92.58 percent of all lithium atoms found in nature are lithium-7 and 7.42 percent are lithium-6, calculate the atomic mass of lithium, Li (atomic number 3). A) 7.0160 amu B) 6.942 amu C) 6.495 amu D) 13.031 amu

Q: The element bromine, Br (atomic number 35), has two major isotopes of similar abundance, both around 50 percent. The atomic mass of bromine is reported in the periodic table as 79.904 atomic mass units. Choose the most likely set of mass numbers for these two bromine isotopes. A) Br-80, Br-81 B) Br-79, Br-80 C) Br-79, Br-81 D) Br-78, Br-80

Q: A beam of protons and a beam of neutrons of the same energy are both harmful to living tissue. The beam of neutrons, however, is less harmful. Why? A) Neutrons are much smaller and lighter than protons and would do less damage. B) Neutrons travel at reduced speed compared to the speed at which protons travel. C) Neutrons carry no electric charge and thus have a greater likelihood of passing through the tissue. D) All of the above are reasons why neutrons are less harmful.

Q: The atomic symbol represents A) the number of electrons in an atom of an element. B) the name of the element. C) the history of the element. D) All of the above. E) Only two of the above.

Q: An element is best described as a material A) consisting of only one type of atom. B) that is pure. C) that has consistent physical properties. D) with more than one type of atom. E) that has consistent chemical properties.

Q: Which of the following images could describe an element at the atomic level? A) B) C) D) none of the images E) all of the images

Q: How do we account for the great variety of substances in the world? A) The Earth is 4.5 billion years old. B) Most of these substances are organic compounds. C) Atoms are incredibly small. D) There are many possible combinations of atoms.

Q: The most massive subatomic particle is the A) electron. B) proton. C) neutron. D) nucleus.

Q: Since atoms are mostly empty space, why don't objects pass through one another? A) The electrons on the atoms repel other electrons on other atoms when they get close. B) The nucleus of one atom repels the nucleus of another atom when it gets close. C) The nucleus of one atom attracts the nucleus of a neighboring atom to form a barrier. D) The electrons of one attract the nucleus of a neighboring atom to form a barrier.

Q: Does it make sense to say that a textbook is about 99.9 percent empty space? A) No. A textbook is a solid and thus is quite dense. Therefore it is not 99.9 percent empty space. B) No. Only gases are considered to be 99.9 percent empty space. Liquids and solids are not. C) Yes. A textbook like all material things is made up of atoms, which are considered to be 99.9 percent empty space. D) No. A textbook could only be considered to be 99.9 percent empty space if it were combusted.

Q: Considering how small atoms are, what are the chances that at least one of the atoms exhaled in your first breath will be in your last breath? A) Not very likely because atoms are constantly dematerializing. B) Not possible at all because atom don't last that long. C) Very probable because atoms are incredibly small. D) There's not really a way that scientists are able to make such an estimate.

Q: In what sense can you truthfully say that you are a part of every person around you? A) We all live on the same planet and share the same resources. B) We are continually exchanging our atoms. C) We all share the same genetic code. D) There are more people alive now than have ever lived.

Q: Where did the atoms that make up a newborn baby originate? A) In the womb of the baby's mother. B) In the digestion of the food that the mother. C) In the Earth through geological processes. D) In the explosions of ancient stars.

Q: Which are older, the atoms in the body of an elderly person or those in the body of a baby? A) a baby because this is surely a trick question B) an elderly person because they have been around much longer C) They are of the same age, which is appreciably older than the solar system. D) It depends upon their diet.

Q: If all the molecules of a body remained part of that body, would the body have any odor? A) Yes, but only if that body is sweating. B) No, because there would be no molecules traveling to our nose. C) Yes, because it would still release photons. D) No, because it would no longer be what it was.

Q: A cat strolls across your backyard. An hour later, a dog with its nose to the ground follows the trail of the cat. Explain what is going on from a molecular point of view. A) The dog is following the areas of increased density of the Earth. B) The dog is smelling atoms from the cat. C) The dog is smelling molecules from the cat. D) The cat is leading the dog into a trap.

Q: Light travels faster in A) thin air. B) dense air. C) same in each.

Q: Light travels faster in A) warm air. B) cool air. C) a vacuum.

Q: When light is refracted, there is a change in its A) frequency. B) wavelength. C) both of these D) neither

Q: If you wish to send a beam of laser light from Earth to a space station above the atmosphere near the horizon, aim your laser A) above your line of sight. B) below your line of sight. C) along your line of sight.

Q: If you wish to spear a small blue fish with a red laser beam, you should compensate for refraction and aim your laser A) directly at the sighted fish. B) above the sighted fish. C) below the sighted fish.

Q: If you wish to spear a red fish with a red laser beam, you should compensate for refraction and aim your laser A) directly at the sighted fish. B) above the sighted fish. C) below the sighted fish.

Q: If you wish to spear a fish with a regular spear, you should compensate for refraction and throw your spear A) directly at the sighted fish. B) above the sighted fish. C) below the sighted fish.

Q: Because of refraction a fish in the water appears A) nearer the surface. B) deeper in the water. C) at its actual depth.

Q: Because of refraction, a person standing waist deep in a swimming pool appears to have A) shorter legs. B) longer legs. C) thinner legs. D) none of the above

Q: Refraction causes the bottom of a swimming pool to appear A) deeper. B) more shallow. C) neither

Q: When a light beam emerges from water into air, the average light speed A) increases. B) decreases. C) remains the same.

Q: A beam of light emerges from water into air at an angle bent A) towards the normal B) away from the normal. C) in a direction parallel to the normal. D) in a direction perpendicular to the normal. E) not at all.

Q: Light changes direction when traveling from air into glass due to changes in light's A) intensity. B) wavelength. C) frequency. D) velocity. E) amplitude.

Q: Refraction results from changes in light's A) frequency. B) incident angles. C) speed. D) all of the above E) none of the above

Q: Refraction occurs when light passing from one medium to another A) changes frequency. B) changes speed. C) loses energy. D) reflects inward.

Q: Ninety-five percent of light incident on a mirror is reflected. How much light is reflected from three mirrors in succession? A) 81% B) 86% C) 90% D) 95%

Q: The Moon's reflected image in a lake often appears as a vertical column when the water is A) perfectly still. B) slightly rough. C) very rough, churning with waves.

Q: When a mirror with a fixed beam on it is rotated through a certain angle, the reflected beam is rotated through an angle A) equal to the angle of rotation. B) twice as much. C) four times as much. D) none of the above

Q: Standing at the shore of a still lake, the reflected view of scenery on the far side of the lake is the view you would see if you were upside down with your eye in the line of sight A) where it presently is. B) at the surface of the water where the light reflects. C) directly beneath you, as far below water level as you are above. D) close to the distant shore. E) none of the above

Q: A diver shines light up to the surface of a smooth pond at a 10 angle to the normal. Some light passes into the air above, and the part that reflects back into the water makes an angle to the normal of A) less than 10. B) 10. C) more than 10.

Q: When you look at yourself in a pocket mirror, and then hold the mirror farther away, you see A) more of yourself. B) less of yourself. C) the same amount of yourself.

Q: In looking at yourself in a steamy mirror you wipe just enough moisture away to barely see a full view of your face. If you move back from the mirror you'll see A) a bit more of your face. B) a bit less of your face. C) the same amount of your face.

Q: To see his full height, Blinky Bill who is 1.0 meter tall needs a mirror that is at least A) 0.33 m tall. B) 0.50 m tall. C) 0.75 m tall. D) 1 m tall. E) depends on distance from the mirror.

Q: The shortest plane mirror in which you can see your entire image is A) half your height. B) 3/4 your height. C) 1/3 your height. D) equal to your height. E) dependent on your distance from the mirror.

Q: A rough surface for infrared waves may be polished for A) radio waves. B) light waves. C) both of these D) neither

Q: Compared to the wavelength of incident light, diffuse reflection occurs when the size of surface irregularities is A) smaller. B) larger. C) about the same.

Q: Diffuse reflection occurs when the size of surface irregularities is A) small compared to the wavelength of the light used. B) large compared to the wavelength of the light used. C) either

Q: If you walk toward a mirror at a certain speed, the relative speed between you and your image is A) half your speed. B) your speed. C) twice your speed. D) none of the above

Q: For a curved mirror, the law of reflection holds for A) the mirror as with a plane mirror. B) tiny segments that act as plane surfaces. C) both convex and concave mirrors. D) only convex mirrors.

Q: The inversion of Marjorie's image in a plane mirror is actually an inversion of A) left and right. B) up and down. C) front and back. D) all of the above

Q: When light reflects from a polished surface, there is a change in its A) frequency. B) wavelength. C) speed. D) all of the above E) none of the above

Q: The amount of light reflected from the front surface of common window glass is about A) 4%. B) 8%. C) 40%. D) 92%. E) 96%.

Q: Object and image for a plane mirror lie A) along the same plane. B) equal distances from the mirror. C) at right angles to each other. D) all of the above E) none of the above

Q: According to the law of reflection, the incident ray, reflected ray, and normal between them A) lie in the same plane. B) may or may not lie in the same plane. C) lie in planes that are perpendicular to one another.

Q: When you read from a printed page, you're seeing reflected light that is A) specular. B) diffuse. C) both of these D) neither of these

Q: The image seen in a plane mirror is due to A) specular reflection. B) diffuse reflection. C) both of these D) neither of these

Q: The reason that a surface appears darker when wet has to do with A) the darkness of liquids. B) conversion of light to lower frequencies. C) absorption of multiply-reflecting light inside the wet region.

Q: Light shines on a pane of green glass and a pane of clear glass. The temperature will be higher in the A) clear glass. B) green glass. C) neither

Q: Which will warm up quicker in sunlight? A) a piece of colored glass B) a piece of clear glass C) both the same

Q: Which becomes warmer in sunlight, sunglasses or clear reading glasses? A) sunglasses. B) reading glasses. C) both of these D) none of the above

Q: Glass is opaque to light with wave frequencies that A) match its natural frequencies. B) are below its natural frequencies. C) both of these D) none of the above

Q: Glass is transparent to light of frequencies that A) match its natural frequencies. B) are below its natural frequencies. C) both of these D) none of the above

Q: Materials generally become warmer when light is A) absorbed by them. B) reflected by them. C) transmitted by them. D) all of the above E) none of the above

Q: Metals are shiny because A) they reflect 100% of incident light. B) they are poor absorbers of light. C) loose electrons vibrate to the oscillations of any incident light. D) none of the above

Q: Compared with the photons of light that shines on glass, the emerging photons are A) the same photons. B) different though identical. C) a mixture of being the same and different.

Q: Infrared waves are often called heat waves because they A) emanate from relatively hot sources. B) consist of frequencies lower than those of visible light. C) induce resonance of molecules in the skin that becomes thermal energy. D) are absorbed rather than reflected by the skin. E) are the predominant waves emitted by the Sun.

Q: Compared with the speed of light in a vacuum, the speed of light in the empty space between molecules in glass is A) more. B) the same. C) less.

Q: Consider light energy that is momentarily absorbed in glass and then reemitted. Relative to the absorbed light, the frequency of the reemitted light is A) less. B) the same. C) more.

Q: Non-reflected ultraviolet light that shines on a pane of transparent glass A) produces a chain of absorptions and re-emissions through the glass. B) transforms to thermal energy. C) is mostly reflected.

Q: When visible light is incident upon transparent glass, most atoms in the glass A) are forced into vibration. B) resonate. C) convert the light energy into thermal energy.

Q: Visible light that shines on a pane of transparent glass A) is mostly reflected. B) produces a chain of absorptions and re-emissions through the glass. C) mostly transforms to thermal energy.

Q: When ultraviolet light is incident upon glass, most atoms in the glass A) resonate. B) pass the light energy along practically undiminished. C) freely absorb and reemit most of the ultraviolet light.

Q: Electrons in glass have a natural frequency in the A) infrared region of the spectrum. B) visible region of the spectrum. C) ultraviolet region of the spectrum.

Q: Relative to its average speed in air, the average speed of a beam of light in glass is A) more. B) the same. C) less.

Q: The distance between Earth and the Moon is 3.84 108 m. A pulse of laser light aimed at the Moon that bounces back to Earth undergoes a round-trip time of about A) zero seconds. B) less than 1 second. C) two and a half seconds. D) three seconds.

Q: If a light signal and a radio signal were emitted simultaneously from the Moon, the first signal to reach Earth would be A) radio. B) light. C) both of these D) none of the above

Q: If a light signal and a radio signal were emitted simultaneously from Alpha Centauri, the first to reach Earth would be the A) radio signal. B) light signal. C) both the same time

Q: An electron vibrating to and fro 1000 times per second generates an electromagnetic wave having a A) period of 1000 s. B) speed of 1000 m/s. C) wavelength of 1000 m. D) frequency of 1000 Hz.

Q: Radio waves travel A) always much faster than sound waves. B) usually at the same speed as sound waves. C) slower, on average, than sound waves. D) at a speed that depends on frequency.

Q: Your friend says that any radio wave travels appreciably faster than any sound wave. A) agree with your friend unconditionally B) agree with your friend for most common cases C) disagree with your friend D) find a new friend

Q: Relative to ultraviolet waves, the wavelength of infrared waves is A) shorter. B) longer. C) the same.

Q: Relative to radio waves, the velocity of visible light waves in a vacuum is A) less. B) more. C) the same.

Q: A wave with a long wavelength has a relatively A) low frequency. B) high frequency. C) both of these D) neither