Physics 262 Final Examination Sp 04 KEY

1. A coil of wire in an AC circuit causes what effect?
1. radiation
2. inductance
3. a lower frequency
4. extra current
5. higher voltage

2. A resistor does not cause any impedance in an AC circuit.

a. True b. False c. you cannot tell d. this is a nonsense question

3. What inductance must be used with a 12 microfarad capacitor to produce a frequency of 11 kHz?
1. 6 exp-4 Farads
2. 7 exp-7 F
3. 7 exp-2 F
4. 1.2 F
5. 4 exp –6 F

4. What direct current will produce as much thermal energy in a resistor as an alternating current that has a maximum value of 2.4A?
1. cannot say without the value of the resistor
2. 2.4 A
3. 1.2 A
4. 1.4 A
5. 1.7 A

5. A transformer on a utility pole operates at 8.5 kV (a.c.) on the input side. It supplies electricity to houses at 120 Volts. (Both voltages are rms). If this is an ideal transformer, no losses and power factor of one, what is the turns ratio N primary/ N secondary ?

1. 120
2. 71
3. 1020
4. 14
5. 0.014

6. A group of electrons executing simple harmonic motion in a wire (forced by an a.c. generator) will:

a. only dissipate energy as heat

b. cause the wire to oscillate

c will cause an EM wave to be radiated

d. will cause a current to flow through the air

e. cause the wire to melt

7. The electromagnetic spectrum is made up of a number of regions, each assigned a name, depending on the wavelengths involved. In order of decreasing frequency these are:

a. radio waves, x-rays, microwaves, visible light, ultraviolet, infrared, gamma rays

b. microwaves, radio waves, infrared, visible, gamma rays, x-rays

c. radio waves, infrared, visible, ultraviolet, x-rays, gamma rays, microwaves

d. radio waves, microwaves, infrared, visible, ultraviolet, x-rays, gamma rays

e. gamma rays, x-rays, ultraviolet, visible, infrared, microwaves, radio waves

8.We see the moon by reflected sunlight. When we see a photon from the full moon, how much . .. … . earlier did it leave the sun? Distances: earth-sun 1.50 exp8 km, earth-moon 3.80 exp5 km

a. it depends on whether it is day or night

b. it depends on the phase of the moon

c. 8 minutes, one and a third seconds

d. 8 minutes, twenty one and a third seconds

e. 8 minutes, twenty two and a half seconds

9. Natural light passed through a polarizing filter has:

1. only Io/3 compared to its original intensity.
2. A greatly reduced B field.
3. Suffered no effect.
4. Lost half of its intensity.
5. Lost intensity depending on the square of the cosine of the angle between the light and the normal to the filter.

For the next six questions use these answers

a. reflection

b. refraction

c. interference

d. dispersion

e. diffraction

10..When light strikes glass at an angle, some is ____b______ through the glass.

11..When you have two apertures in the same opaque plane and illuminated by coherent light, you will find an______c_________ pattern on a screen at a distance in front of the apertures.

12. ______e_________ is understood best in terms of Huygen’s radiators at every point on a wavefront.

13.. When a light ray emerging from under water reaches the surface, it will appear to come from a point shallower than it really comes from due to__b______.

14.. Shimmering bands of color on the surfaces of soap bubbles are due to _____c________

15..The separation of white light into colors by a prism is due to _____d________.

16. Radiation pressure on a particle by a light source depends on the ______and _____ the particle.

a. pressure repells

b. intensity attracts

c. color repells

d. intensity repells

e..light cannot exert a force on a particle

17. A fish in a pond on a sunny day sees _______ because of __________.

a. darkness dispersion

b. all of the light that hits the water refraction

c. a circle of light above total internal reflection

d. a circle of light above total external reflection

e. a rainbow of colors covering its field of view dispersion

18. When light travels from medium X to medium Y as shown:

a..both the speed and the frequency decrease

b..both the speed and the frequency increase

c..both the speed and the wavelength decrease

d..both the speed and the wavelength increase

e..We cannot say what happens—we are not told the value of indices of refraction.

19. An object is 20 cm to the left of a thin diverging lens having a 30 cm focal length. What is the image

distance? Show in a diagram also.

1. 20 cm to right of lens
2. 30 cm to left of lens
3. 12 cm to right of lens
4. 12 cm to left of lens
5. 6 cm to left of lens

20. A virtual image is one:

a. toward which light rays converge but do not pass through

b. from which light rays diverge but do not pass through

c. from which light rays diverge as they pass through

d. toward which light rays converge and pass through

e. you cannot see

21. A soap film, 4 exp-5 cm thick, is illuminated by white light, normal to its surface. The index of refraction of the film is 1.50. Which wavelengths will be intensified in the reflected beam?

a. 400nm and 600nm

b. 480nm and 800nm

c. 360nm and 533 nm

d. 400nm and 800nm

6. 510nm and 710nm

22. Bragg’s Law for x-ray diffraction from a crystal is 2dsinq = ml , where the quantity d is the:

a. height of the unit cell

b. smallest interatomic distance

c. distance from detector to sample

d. distance between the planes of atoms

6. usual calculus symbol for a differential

23. If you look through a telescope at a clock (identical to your clock) on a moving satellite, what will you observe? a. it will appear to be running slow because of the effects of S.R.

b. it will appear to be running fast due to the effects of S.R.

c. it might appear to be running either fast or slow, due to Doppler effect

d. it will be running at the same rate because if you are looking at it, it is in your FOR

e. this is a general relativity problem—we cannot say

24. If you are on a spaceship moving at 0.4c past a planet, the diameter of the planet will appear to be:

a. only 0.4 of what it is in its own frame

b. the same as in its own frame, because as you pass, for a moment, you are in its frame

c. 1.4 times its proper length

d. 92% of its proper length

e. 84% of its proper length

25. An observer notes a moving clock is running slow by a factor of ten (not a Doppler effect).

What is the gamma of the clock with respect to the observer?

a. 0.990 c

b. 10

c. 0.900c

d. 1/10

e. 10c

26. A quasar is observed from a spaceship that is traveling at 0.2 c away from the Earth and toward the quasar. The ship reports to Earth that they observe a spectral line shifted from its proper wavelength at the quasar 450nM to a wavelength of 1200nM. What is the velocity of the quasar with respect to the Earth? (in terms of c) Show work and use diagram.

1. 0.22c
2. 0.37c
3. 0.57c
4. 0.83c
5. 0.91c

27. The energy carried by a single photon

1. cannot be calculated
2. is given by hf
3. is given by hc
4. is given by cf
5. is too small to measure

28… Light of a wavelength of 2.4 pm is directed onto a target containing free electrons. What will happen?

a. the light will all be absorbed

b. the light will pass through unaffected

c. the light will scatter off of the electrons

d. the light will cause all of the electrons to fly out of the target

29. What is the DeBroglie wavelength of an electron (in a TEM) that has energy of one keV?

a. 3.9 exp-11 m

b. 2.3 exp 12 m

c. 2.4 exp-13 m

d. 1.2 exp-9 m

30…An electron is trapped in a one dimensional, infinite potential well with a width of L = 100 pm.

What will happen?

a. the electron will drop down to the bottom of the well

b. the electron will be able to tunnel sometimes

c. the electron will only be allowed in discrete energy levels

d. the electron will escape from the well

e. the electron will lose its charge

31…In the Bohr model of the atom, the electrons have discrete energies and

a. DeBroglie wavelengths

b. orbits

c. probabilities

d. sizes

e. closed shells

32…In modern theory, to completely describe the energy state of an electron in an atom, we need

a. five quantum numbers

b. two quantum numbers

c. four quantum numbers

d. depends on the size of the atom

33…In Schrodinger’s equation, the wave function, Y(x,t), tells us the

a. wavelength of the particle

b. probability of finding the particle

c. width of the potential well

d. the wavelength, if it is squared

e. the probability density, when squared

34…Barrier tunneling in the nucleus of some atoms explains

a. the energies of the electrons in sub shells

b. radioactive a decay

c. the colors of the elements

d. gamma decay

35…The position of an element in the periodic table of elements depends on

a. its size

b. its atomic weight

c. its atomic number

d. its magnetic dipole moment

36… What is the total number of quarks and antiquarks in our Standard Model of particle physics?

a. 6 b. 12 c. 18 d. 36 e. 72

37….The up and down quarks are found

a. in ordinary nucleons

b. only in cosmic rays

c. only in astrophysical situations

d. free in the nuclei of some atoms

38…The element with the highest binding energy per nucleon is

a. hydrogen

b. helium

c. iron (or an isotope of nickel)

d. lead

e. uranium

39…Fusion power will be most likely accomplished with

a. uranium

b. plutonium

c. neon and krypton

d. hydrogen and helium

e. electrons

40…Stars are powered by a. fusion b. fission c. carbon decay d. chemical reactions

41…The most abundant element in the universe is

a. iron

b. neutrons

c. uranium

d. helium

e. hydrogen

42…The original elements were formed in the first ____ after the big bang.

a. Planck time

b. few nanoseconds

c. few microseconds

d. few seconds

e. few hundred seconds

43…We cannot see back in time any further than when the universe was at a temperature of

a. 300,000K

b. 30,000K

c. 3,000K

d. 300K

e. 3K

44…Due to the MAP satellite we now know the age of the universe is approximately

a. 20 billion years

b. 13 billion years

c. 9 billion years

d. 20 million years

e. 13 million years

Have a good summer. Take care of yourself. J