**UNIVERSITY OF GUELPH**

**PHYS*1130 W'92**

**Physics with Applications II**

**SAMPLE FINAL EXAMINATION 2**

For multiple choice click on the correct answer for the solution.

1) The equation for a certain standing wave on a string is:

y = 5X10^{-3}(cos 2t)sin 16x

What is the approximate length of the shortest string that could be
used? The amplitude and x are in metres and t is in seconds.

A) 0.5 m

B) 0.6 m

C) 0.4 m

D) 0.3 m

E) 0.2 m

2) Two travelling waves,

y = 0.10 sin(3t + 4px) metres

and

y = 0.20 sin(3t - 5px) metres

meet at t = 0. What is the displacement at x = 4.5 m?

A) 0.14 m

B) 0 m

C) -0.20 m

D) -0.14 m

E) 0.20 m

3) The intensity level 5.0 m from a speaker is 75 db. What
acoustical
power would pass through a rectangular opening (2.0 m x 1.0 m) in a
wall
at this distance from the speaker? Assume that the speaker is a point
source
radiating in all directions.

A) 6.32 x 10^{-5} W

B) 7.98 x 10^{-5} W

C) 4.85 x 10^{-4} W

D) 1.36 x 10^{-6} W

E) 1.78 x 10^{-6} W

4) A whistle is emitting a frequency of 1000 Hz. You approach it at
a speed of 4.00 m s^{-1}. What frequency will you hear?

A) 1012 Hz

B) 980 Hz

C) 1020 Hz

D) 1000 Hz

E) 1004 Hz

5) A black body at 800 K sits in a room at 27º C. Its surface area
is 3.00 m^{2}. What net power does it radiate? (Stefan's
constant
is 5.62X10^{-8} WK^{-4}m^{-2})

A) 3.65 x 10^{3} W

B) 4.98 x 10^{3} W

C) 2.63 x 10^{4} W

D) 6.83 x 10^{4} W

E) 3.95 x 10^{5} W

6) A city is at 50º south latitude. At noon on a certain day, the
Earth's axis of rotation is tilted 10º towards the Sun (i.e., the
N pole is closer to the Sun than the S pole). What is the angle q
you would use to calculate the average solar intensity at this city at
this time?

A) 20 º

B) 30º

C) 40º

D) 50º

E) 60º

7)

A beam of light enters side 1 of a triangular piece of plastic (a prism) of index of refraction 1.5 as shown. The three sides of the prism are of equal length. Which of the following statements is correct? |

A) The beam will emerge from side 1.

B) The beam will emerge from side 2.

C) The beam will emerge from side 3.

D) The beam will not emerge.

E) The problem cannot be solved because the wavelength of the light
has not been given.

8)

A glass hemisphere of radius 5 cm is placed over a spot on a table and viewed from above. Where does the spot appear to be? |

A) 5 cm below the top of the hemisphere.

B) At the top surface of the hemisphere.

C) 2.5 cm above its real position.

D) 5 cm above the top of the hemisphere.

E) At infinity.

9) Determine the wavelength of an n = 3 electron in a linear
conjugated
p-system of length 1.05 nm.

A) 0.4 nm

B) 0.7 nm

C) 2.1 nm

D) 2.8 nm

E) 4.5 nm

10) If the chromophore of question 9 contained 8 carbon atoms, what
is the probability density of the n = 3 electron at the 2^{nd}
or the 7^{th} carbon atom.

A) 2.4 nm^{-1}

B) 1.8 nm^{-1}

C) 3.2 nm^{-1}

D) 0.6 nm^{-1}

E) 4.8 nm^{-1}

11) A toaster is rated at 700 watts when plugged into a 115 volt
(rms)
circuit. Determine the resistance of the toaster.

A) 11.3 W

B) 0.16 W

C) 18.9 W

D) 2.80 W

E) 5.11 W

12) The radioactive decay product of ^{15}_{8}O is (^{15}_{8}O
decays by beta-decay):

A) ^{15}_{9}F

B) ^{16}_{8}O

C) ^{14}_{9}F

D) ^{14}_{7}N

E) ^{15}_{7}N

13) Determine the maximum kinetic energy of the -ray in the
radioactive
decay of ^{31}_{14}Si. The mass of the electron is
0.000550
amu.

A) 7.3 x 10^{-11} J

B) 2.4 x 10^{-13} J

C) 1.6 x 10^{-13} J

D) 4.9 x 10^{-14} J

E) 9.2 x 10^{-12} J

Atomic number Z | Element symbol | Mass number A | Atomic mass |

12 | Mg | 24 | 23.985045 |

13 | Al | 27 | 26.981541 |

14 | Si | 28 | 27.976928 |

14 | Si | 31 | 30.975364 |

15 | P | 31 | 30.973763 |

15 | P | 32 | 31.973908 |

16 | S | 32 | 31.972072 |

14) Suppose that 2 years after a spill of radioactive tritium ( ^{3}_{1}
T) into Lake Ontario a count rate of 670 counts/hour is obtained from a
10 ml sample of lake water. After another 2 years, the count rate from
a similar sample is 410 counts/hour. If all the non-radioactive
clearance
processes (river outflow, evaporation, absorption into lake mud, etc.)
can be assumed to have a half-life T_{x}, determine T_{z}.
(Assume that complete mixing of the tritium throughout the lake has
occurred.
The radioactive half life of tritium is 12.33 yr)

A) 0.7 yrs

B) 1.7 yrs

C) 2.7 yrs

D) 3.7 yrs

E) 4.7 yrs

15) Which one of the following statements is __false__?

A) The light radiated by the Earth is primarily in the infrared
region
of the electromagnetic spectrum.

B) The greenhouse effect is due to the fact that the atmosphere is
clear
to incoming radiation in the ultraviolet and visible, but opaque to
outgoing
radiation in the infrared.

C) The main problem with excess CO_{2}
is that it increases atmospheric absorption in the near-ultraviolet
region
of the electromagnetic spectrum.

D) Determination of the Earth's albedo (the fraction of sunlight
reflected
to that absorbed) can be made by examining the moon at first or third
quarter.

E) Some anthropogenic gases such as the chlorofluorocarbons can
contribute
to the greenhouse effect.

16) A crude telescope is constructed of 2 thin lenses of focal length 50 cm and 15 cm (the eyepiece) in air. The lenses are of glass of index of refraction 1.6. The front surface of the objective is placed just under the surface of a remarkably clear lake. What now will be the new separation between the lenses if both object viewed and the final image are at infinity? (Assume both surfaces of the objective have the same magnitude of radius of curvature. The index of refraction of water is 1.33)

17) A spring is suspended vertically from the ceiling. When a mass of 2.0 kg is hung on the end of the spring, the mass lowers 25 cm before it reaches its new equilibrium position. The mass is then raised 20 cm above the equilibrium position and released. Find the velocity of the mass the second time it is 10 cm below the equilibrium position.

18) A manufacturer of plastics needs to make a light filter which
will
absorb 80% of the photons (l = 488 nm)
striking
it. A measurement on a sample piece of the plastic 1.0 cm thick
indicated
that 30% of the photons striking it were absorbed.

(a) Determine the pathlength (thickness) required to absorb 80% of the photons.

(b) Determine absorbance of the plastic which absorbs 80% of the photons.