Physics

Front 1

Light goes from material having a refractive index of n1 into a material with refractive index n2. If the refracted light is bent away from the normal, what can you conclude about the indices of refraction?

Back 1

n1 > n2

Front 2

A thin flashlight beam traveling in air strikes a glass plate at an angle of 52° with the plane of the surface of the plate. If the index of refraction of the glass is 1.4, what angle will the beam make with the normal in the glass?

Back 2

26°

Front 3

A glass plate with an index of refraction is 1.57 is immersed in an oil having a refractive index of 1.40. The surface of the glass is inclined at an angle of 54° with the vertical. A horizontal light ray in the glass strikes the interface. What is the angle that the refracted ray, in the oil, makes with the horizontal?

Back 3

11°

Front 4

An object is placed to the left of a spherical mirror in front of the mirror. If the image of the object is formed on the right side of the mirror, which of the following statements must be true? (There could be more than one correct choice.)

Back 4

The image is upright and virtual.
The mirror could be either concave or convex.

Front 5

An object is placed in front of a convex mirror at a distance larger than twice the magnitude of the focal length of the mirror. The image will appear

Back 5

upright and reduced.

Front 6

A beam of light that is parallel to the principal axis strikes a concave mirror. What happens to the reflected beam of light?

Back 6

It passes through the focal point of the mirror.

Front 7

A beam of light that is parallel to the principal axis strikes a convex mirror. What happens to the reflected beam of light?

Back 7

It appears to be coming from the focal point on the other side of the mirror.

Front 8

A convex lens has focal length f. If an object is placed at a distance of 2f from the lens on the principal axis, the image is located at a distance from the lens

Back 8

of 2f.

Front 9

A convex lens has focal length f. If an object is placed at a distance beyond 2f from the lens on the principal axis, the image is located at a distance from the lens

Back 9

between f and 2f.

Front 10

Starting from very far away, an object is moved closer and closer to a diverging lens, eventually reaching the lens. What happens to its image formed by that lens? (There could be more than one correct choice.)

Back 10

The image keeps getting larger and larger.
The image always remains virtual.
The image gets closer and closer to the lens.

Front 11

Which of following statements about the image formed by a single converging lens are true?

Back 11

None of the above choices are correct.

Front 12

Which of following statements about the image formed by a single diverging lens are true? (There could be more than one correct choice.)

Back 12

The image is always virtual.
The image is always upright.

Front 13

An object is placed in front of a thin lens. Which statements are correct in describing the image formed by the lens?

Back 13

If the image is real, then it is also inverted.
If the lens is concave, the image must be virtual.

Front 14

If the lens in a person's eye is too highly curved, this person is suffering from

Back 14

nearsightedness.

Front 15

If the back of a person's eye is too close to the lens, this person is suffering from

Back 15

farsightedness.

Front 16

Nearsightedness is usually corrected with

Back 16

diverging lenses.

Front 17

Farsightedness can usually be corrected with

Back 17

converging lenses.

Front 18

A little known fact is that both Robinson Crusoe and Friday wore eyeglasses. As it so happens, Robinson Crusoe was farsighted while Friday was nearsighted. Whose eyeglasses did they use whenever they wanted to start a fire by focusing the sun's rays?

Back 18

Robinson Crusoe's

Front 19

For relaxed viewing with a microscope or a telescope, the eyepiece is adjusted to place the image at

Back 19

infinity.

Front 20

What type of lens is used to make a magnifying glass?

Back 20

converging

Front 21

Which one of the following is a characteristic of a compound microscope?

Back 21

The image formed by the objective is real.

Front 22

In an electromagnetic wave in free space, the electric and magnetic fields are

Back 22

perpendicular to one another and perpendicular to the direction of wave propagation.

Front 23

Which one of the following types of electromagnetic wave travels through space the fastest?

Back 23

They all travel through space at the same speed.

Front 24

If unpolarized light of intensity I0 passes through an ideal polarizer, what is the intensity of the emerging light?

Back 24

I0/2

Front 25

For a beam of light, the direction of polarization is defined as

Back 25

the direction of the electric field's vibration.

Front 26

Increasing the brightness of a beam of light without changing its color will increase

Back 26

the number of photons per second traveling in the beam.

Front 27

If the wavelength of a photon is doubled, what happens to its energy?

Back 27

It is reduced to one-half of its original value.

Front 28

Which of the following actions will increase the energy of a photon?

Back 28

Decrease its wavelength.

Increase its frequency.

Front 29

The Balmer series is formed by electron transitions in hydrogen that

Back 29

end on the n = 2 shell.

Front 30

To which of the following values of n does the longest wavelength in the Balmer series correspond?

Back 30

3

Front 31

To which of the following values of n does the shortest wavelength in the Balmer series correspond?

Back 31

∞ (very large)

Front 32

The energy difference between adjacent orbit radii in a hydrogen atom

Back 32

decreases with increasing values of n.

Front 33

The figure shows part of the energy level diagram of a certain atom. The energy spacing between levels 1 and 2 is twice that between 2 and 3. If an electron makes a transition from level 3 to level 2, the radiation of wavelength λ is emitted. What possible radiation wavelengths might be produced by other transitions between the three energy levels?The figure shows part of the energy level diagram of a certain atom. The energy spacing between levels 1 and 2 is twice that between 2 and 3. If an electron makes a transition from level 3 to level 2, the radiation of wavelength λ is emitted. What possible radiation wavelengths might be produced by other transitions between the three energy levels?

Back 33

both λ/2 and λ/3

Front 34

The distance between adjacent orbits in a hydrogen atom

Back 34

increases with increasing values of n.

Front 35

The orbital angular momentum quantum number can take which of the following values for any given value of the principal quantum number, n?

Back 35

ℓ = 0, 1, 2, . . . , (n - 1)

Front 36

According to the quantum mechanical model of the hydrogen atom, if the orbital angular momentum quantum number is , there will be how many permitted magnetic quantum numbers?

Back 36

2 + 1

Front 37

According to the quantum mechanical model of the hydrogen atom, if the principal quantum number is n, how many different orbital angular momentum quantum numbers are permitted?

Back 37

n

Front 38

The magnetic quantum number m1 can have any integer value ranging from

Back 38

-ℓ to +ℓ.

Front 39

The symbol for a certain isotope of polonium is 214/84Po. How many neutrons are there in the nucleus of this isotope?

Back 39

130

Front 40

A stable nucleus contains many protons very close to each other, all positively charged. Why do the protons not fly apart due to mutual Coulomb repulsion?

Back 40

An attractive nuclear force in the nucleus counteracts the effect of the Coulomb forces.

Front 41

In massive stars, three helium nuclei fuse together, forming a carbon nucleus, and this reaction heats the core of the star. The net mass of the three helium nuclei must therefore be

Back 41

higher than that of the carbon nucleus.

Front 42

A radioactive isotope of atomic number Z emits an alpha particle, and the daughter nucleus then emits a beta-minus particle. What is the atomic number of the resulting nucleus?

Back 42

Z -1

Front 43

The atom 223/87Fr decays to 223/88Ra by emitting what kind of nuclear radiation?

Back 43

beta-minus

Front 44

The half-life of cobalt-60 is 5.3 years, while that of strontium-90 is about 29 years. Suppose you have samples of both isotopes, and that they initially contain equal numbers of atoms of these isotopes. How will the activities (number of decays per second) of the samples compare?

Back 44

The activity of the cobalt-60 sample will be greater.

Front 45

If the half-life of a material is 45 years, how much of it will be left after 100 years?

Back 45

less than 1/4 but more than 1/8

Front 46

What happens to the half-life of a radioactive substance as it decays?

Back 46

It remains constant.

Front 47

Two radioactive isotopes, X and Y, both decay to stable products. The half-life of X is about a day, while that of Y is about a week. Suppose a radioactive sample consists of a mixture of these two nuclides. If the mixture is such that the activities arising from X and Y are initially equal, then a few days later the activity of the sample will be due

Back 47

predominantly to Y.

Front 48

Suppose the half-life of an isotope is 2 days. You purchase 10 grams of the isotope, but it was produced in a laboratory 4 days before it was delivered to you. How much of this isotope will you have 3 days after it was delivered to you?

Back 48

less than 1.25 grams

Front 49

Modern in-air nuclear bomb tests have created an extra high level of 14C in our atmosphere. If future archaeologists date samples from this era, without knowing of this testing, will their carbon-14 dates be too young, too old, or correct? If correct, why?

Back 49

Too young.

Front 50

How does modeling the leg as a pendulum help explain the speed at which we walk?Your answer does not need to include any equations (though it can), but you should mention the concept of the "natural period" of a pendulum, and what determines it.

Back 50

The natural period of a physical pendulum is given by T=2(pie)sqrt(I/mgd)) Because our legs swing forward with each step we take, they can be modeled as physical pendulums. And because the moment of inertia of a rod is given by I=mL2/3, we have T=2(pie)squart(2L/3g). If we assume a typical leg length of 1.0m, this gives T=1.64 s, which implies a step every .8 s, which is close to what we actually observe. Because this model works so well, we can assume that a large part of the reason we naturally walk at the speed we do is to conserve energy- we are letting gravity swing our legs forward.

Front 51

Explain the phenomenon of resonance. How is resonance important to our sense of hearing?

Back 51

When you drive an oscillating system at its natural frequency, it will oscillate with high amplitude, or resonate. In order to hear, pressure waves cause the ear drum to vibrate, and these vibrations are then amplified by a series of bones that ultimately cause the basilar membrane (inside the cochlea) to vibrate. The basilar membrane can be thought of as a string whose tension and mass density vary along its length, so that different parts of the “string” resonate at different frequencies (according to the equation (f1=1/2L*sqrt(I/u). Hair cells within the basilar membrane cause neurons to fire when they vibrate with large amplitude, so that when specific parts of the basilar membrane resonate in response to specific frequencies of sound, specific sets of neurons fire.

Front 52

Why are you relatively safe inside a car during a thunderstorm?

Back 52

Because all excess charge resides on the surface of a conductor. This means that cars made of metal (which are most, but not all cars) effectively act as a shield, preventing the deluge of electrical charge in a lightening bolt from passing through your body. The insulating rubber tires are not thick enough to provide any protection.

Front 53

Explain why a neuron has a resting membrane potential of-70 mV. Yourexplanation should include where the positive and negative charge is located, and where we define to V = 0 to be.

Back 53

We define v=0 outside the neuron. At rest, positive charge accumulates on the exterior surface of a neuron’s cell membrane, and negative charge accumulates on the interior of the membrane. This results in an E-field that points toward the interior of the cell, which means the electric potential must be lower inside the cell compared to outside the cell. Therefore the electric potential must be negative inside the cell.

Front 54

Describe the procedure for hooking up the cables to jump-start a car. What is the worstpossible order to hook up the cables?

Back 54

1. Attach on cable to the positive terminal of the dead battery. 2. Attach the other end of the same cable to the positive terminal of the live battery. 3. Attach one end of the other cable to the negative terminal of the live battery. 4. Attach the other end of the second cable to the engine block of the dead car. The worst possible thing you can do is make the first two connections to the positive and negative terminals of either battery. In this case, accidentally touching the dangling ends together would cause a short circuit.

Front 55

How do electric motors work? What must be done to make sure that the coil continuouslyspins, rather than just oscillates back and forth?

Back 55

Electric motors work by placing a coil of wire in a magnetic field, then running a current through the wire. The direction of the current must be reversed every half-turn in order to get the coil to spin continuously.

Front 56

How does MRI work?

Front 57

How do generators convert mechanical energy into electrical energy? Explain why theyproduce AC current, rather than DC current.

Back 57

A generator consists of a loop of wire that is spun within a constant magnetic field. Faraday’s law results in a current being generated within the loop. By continually spinning the loop within the magnetic field, the magnetic flux through the loop continually goes through cycles of increasing and decreasing, which results in the current continually changing direction (which is the definition of AC current).

Front 58

How are radio waves produced? Describe the difference between AM and FM radio waves

Back 58

Radio waves are produced by applying a sinusoidal voltage to an antenna. Shaking up electrical charge produces electromagnetic waves. In AM radio waves, the signal is encoded in the fluctuating amplitude of the waves, while in FM radio waves the signal is encoded in the fluctuating frequency of the wave.

Front 59

Why does a pencil appear to be broken when you put it in a glass of water? You should drawray diagrams to help explain this.

Front 60

What causes farsightedness, and what kind of lens is needed to correct for it? Whatcauses nearsightedness, and what kind of lens is needed to correct for it?