General Physics III Final Exam Question 1 Question 2 Question 3 ...

NameSecton (circle one) 1 2 3General Physics III Final ExamQuestion 1A temperature of 25 ◦ C is the same as:a) 310 ◦ K;b) 190 ◦ K;c) 77 ◦ F ;d) 97 ◦ F .Question 2A temperature of 45 ◦ C is the same as:a) 113 ◦ F ;b) 57 ◦ F ;c) 300 ◦ K;d) 81 ◦ F .Question 3Wednesday June 10th, 2009 9:45 am 300 BRProfessor MeadowsA hole of diameter 2 cm is drilled in a 2 mm thick square steel plate of side 3 cm.Immediately after drilling, the plate is 30 ◦ C above room temperature. What is thediameter of the hole when the steel cools back down to room temperature?a) 2 − 33 × 10 −5 cms;b) 2 − 66 × 10 −5 cms;c) 2+33× 10 −5 cms;d) 2+66× 10 −5 cms.[α steel =11× 10 −6◦ C −1 ]Question 4When water boils, its molecules:a) gain kinetic energy;b) gain potential energy (from intermolecular forces);c) become “hotter”;d) become colder.[You may assume that boiling takes place at 100 ◦ C.]Question 5The average kinetic energy of the molecules in an object increases with its temperature:

a) True;b) False.Question 6A liquid sample, with mass 1 gm, has specific heat 0.8 (cal/gm·◦C) and latent heat ofvaporization 20 cal/gm. It is at 70 ◦ C and its boiling point is 80 ◦ C.On addition of 30 cals of heat, the sample will:a) all boil;b) partially boil;c) warm up, but not reach the boiling point;Question 7Two moles of an ideal gas have temperature T = 400 ◦ K and pressure P =10 5 N/m 2 .The volume it occupies is:a) less than 1 liter;b) more than 40 liters;c) more than 1 and less than 40 liters;d) about 665 m 3 .[R =8.314 J/mol·K.]Question 85 × 10 4 Joules of heat are added to a system, causing its volume V to increase byΔV =0.1 m 3 . The external pressure is constant at P =10 5 N/m 2 .The internal energy of the system increases by ΔU int =:a) −4 × 10 4 J;b) 4 × 10 4 J;c) 6 × 10 4 J;d) −6 × 10 4 J.Question 9A house in Maine has a glass window with area A and thickness t. The outsidetemperature is −20 ◦ C. At the same time, a house in Florida, with outside temperature+10 ◦ C has a window made from the same glass but with area 2A and thickness t/2.If both houses are maintained at the same temperature of +20 ◦ C, then the heat lostby conduction through the window in Maine is:a) twice;b) 4 times;c) half;

d) one quarter;e) the same asthat through the window in Florida.Question 10A An ideal gas is at 200 K. In order to double the rms speed of its molecules, we needto raise the temperature to:a) 400 K;b) 283 K;c) 800 K;d) 1,130 K;e) 566 K.Question 113 kg-moles of an ideal gas expand irreversibly, at a constant temperature, to 10 timesthe original volume. The change in entropy (in J/K) is about:a) 0;b) 14;c) 1,100;d) 1.3 × 10 4 ;e) None of the above are close to being right.[A kg-mole is a sample whose mass in kg is equal to its molecular weight.]Question 12On a hot day, you come home and, with all the windows shut, you simply open therefrigerator door! The second law of thermodynamics can be used to predict the resultthat:a) the entropy of the room and refrigerator will decrease;b) the temperature of the room and the refrigerator will both decrease;c) the temperature of the room and the refrigerator will reach an equilibrium at atemperature between their initial temperatures;d) the work done by the refrigerator pump will increase the temperature of boththe room and the refrigerator.You may assume that no heat is transferred to or from the environment outside theroom.Question 13At low density and normal room temperatures, H 2 behaves like an ideal, diatomic gaswith molecular weight 2. The heat required to raise the temperature of 4 gms. H 2 by2 K iat constant volume is:a) 200 cals;

) 20 cals;c) 50 cals;d) 0.5 cals.Question 14A machine draws heat from its source at 227 ◦ C and expels its exhaust at 27 ◦ C. Themaximum efficiency that is possible is:a) 200/227;b) 200/27;c) 5/3;d) 40%;e) 300/500.Question 15The Sun’s outer “surface” (the “photosphere”) acts like a black body with temperatureT = 6, 000K that radiates heat, some of which is absorbed by the Earth. If someastronomical disaster were to occur, and the Sun’s photosphere were to cool to 5, 000K,the heat absorbed by the Earth would decrease by a factor:a) 5/6;b) (5/6) 2 ;c) (5/6) 4 ;d) (1/6) 4 .Question 16Which is correct:a) Any periodic wave can be polarized;b) Only transverse waves can be polarized;c) Only longitudinal waves can be polarized.Question 17Adisturbancey(m) in a rod at time t(s) and at a distance x from the end of the rodis given by:y(x, t) =3× 10 −5 sin(0.1x − 314.159t)The speed of propagation of the disturbance isa) 3 × 10 −7 /3.14159 m/s;b) 0.1/314.159 cm/s;c) 3.14159 × 10 3 m/sd) 3 × 10 −5 m/s

Question 18Adisturbancey(m) in a rod at time t(s) and at a distance x from the end of the rodis given by:y(x, t) =3× 10 −5 sin(0.1x − 314.159t)The maximum speed of the medium (∂y/∂t) atanytimeisabouta) 9.4 × 10 2 m/s;b) 9.4 × 10 −3 m/s;c) 3.14159 × 10 −3 m/sd) 3 × 10 −5 m/sQuestion 19A stretched string has mass is μ =0.2 gm per m of length and tension T =8N. Thespeed of propagation of a travelling wave in the string is about:a) 400 m/s;b) 200 m/s;c) 250 m/sd) None of these is close.Question 20A wave with frequency 1,000 Hz and amplitude 3 mm propagates with speed 250 m/sin a string whose mass is 0.05 gm per m. The power in the wave is abouta) less than 1 W;b) between 1 and 3 W;c) more than 5 and less than 10 W;d) None of these is close.Question 21A sound wave is measured to have intensity 0.098 μW/m 2 .wave isa) -5 dB;b) 5 dB;c) 25 dB;d) 50 dB.The sound level of theQuestion 22A siren whose true frequency is 990 Hz is moving directly towards a stationary observerat a speed of 34 m/s. The apparent frequency heard by the observer is:a) 891 Hz;

) 900 Hz;c) 1.089 KHz;d) 1.1 kHz;e) None of these.Question 23A string (clamped at both ends) has a fundamental frequency of 400 (Hz). In orderto increase the fundamental to 600 (Hz) the length would have to bea) increased by a factor √ 1.5;b) reduced by a factor √ 1.5;c) reduced by a factor 1.5;d) increased by a factor 1.5.Question 24A column of air open at one end and closed at the other has a fundamental frequencyof 1500 (Hz). Which of the following frequencies is a harmonic?a) 500 Hz;b) 2.5 kHz;c) 3.0 kHz;d) 4.5 kHz;e) None of these.Question 25Two waves produce “beats” with frequency 8 Hz.1,204 Hz. The other has frequencya) 1,200 Hz;b) 1,204 Hz;c) 1,208 Hz;d) 1,212 Hz;e) either a) or c).One of the waves has frequencyQuestion 26Two waves of the same frequency have intensities I 1 and I 2 and amplitudes A 1 and A 2 ,respectively. Each intensity is proportional to the square of the amplitude:I 1 = rA 2 1 ; I 2 = rA 2 2where r is the same for both waves. When the waves interfere, the maximum intensitycan be as large as:a) I 1 + I 2 ;

) (I 1 + I 2 ) 2 ;c) r(A 2 1 + A2 2 );d) r(A 1 + A 2 ) 2 .Question 27An electromagnetic wave is propagating horizontally towards you. At a certain instantin time, the ⃗ E-field at some point is vertically upward. The magnetic field at that samepoint, and at that exact same instant isa) vertically downward;b) horizontal and to your left;c) vertically upward;d) horizontal and to your right.Question 28Electromagnetic waves carry energy (like all waves). The intensity (W/m 2 ) is equalto the time-averaged Poynting vector Save =0.5(Emax × Bmax)/μ 0 . If the maximumelectric field is 10 −3 V/m, the intensity is abouta) 1.3 × 10 −9 W/m 2 ;b) 2.7 × 10 +8 W/m 2 ;c) 1.3 × 10 −18 W/m 2 ;d) 2.4 × 10 −8 W/m 2 .[μ 0 =4π × 10 −7 T·m/A; c =3× 10 8 m/s.]Question 29The frequency for visible light with wavelength 500 nm propagating in a vacuum isapproximatelya) 6 × 10 15 Hz;b) 6 × 10 14 Hz;c) 1.67 × 10 15 Hz;d) 1.67 × 10 −16 Hz.[c =3× 10 8 m/s.]Question 30Electromagnetic radiation of frequency 10 13 Hz is labelled asa) radio;b) infra-red;c) ultraviolet;d) gamma ray.

Question 31Huygen’s principle for wave motion:a) can not be applied to plane waves;b) requires a single source of light;c) tells you how to find additional wave fronts, given one wave front;d) relates the frequency, wavelength and velocity of the wave.Question 32A person looks in a mirror and his image just fits the mirror. (This means a ray oflight from the top of his head, after reflection at the top edge of the mirror, enters hiseye, with a similar situation for light from his feet).This means that the vertical dimension of the mirror isa) equal to his height;b) equal to 1/2 his height;c) equal to 1/3rd his height;Question 33Light is incident upon a parallel-sided block of glass (n = √ 3) at an angle of incidenceof 60 ◦ . It willa) emerge from the other side of the glass block, but with a different direction fromits original entry;b) do as in a), but in exactly the same direction and slightly displaced;c) be totally reflected inside the block, and re-emerge from the first side;d) pass straight through the block, as if it were not there.Question 34As light enters a denser medium (ie one with larger refractive index)a) its frequency increases;b) its wavelength increases;c) its colour changes;d) none of the above.Question 35A totally reflecting prism, illustrated in the figure, has angles 45 ◦ -45 ◦ -90 ◦ . In order towork in air, the index of refraction for the prism material cannot be less than

a) 1/ √ 2;b) √ 2;c) tan 45 ◦ .Question 36A real image 8 times the size of a real object is formed by a single lens. The objectto image distance is 81 cm. The focal length of the lens is thereforea) +16 cm;b) -8 cm;c) +48 cm;d) +8 cm;e) None of these.Question 37A smart student in the laboratory wants to see if a lens is convex or concave. To testthis, she holds the lens near a wall that is opposite the window, and she sees an imageof objects far away (outside the window) clearly focussed on the wall. The lens she istesting isa) concave;b) convex;c) this test is not conclusive.Question 38A far-sighted (“hypermetropic”) person can focus objects only if they are further fromtheir eye than 1 m. A person with “normal” vision can focus objects that are furtherthan 0.25 m. To restore normal vision, the far-sighted person will need a correctivelens in front of their eyes that isa) concave;b) convex.Question 39The image of a real object that is 10 cm in front of a concave spherical mirror withradius 30 cm is

a) virtual, right way up and behind the mirror;b) real, right way up and behind the mirror;c) virtual, upside down and in front of the mirror;a) real, upside down and in front of the mirror.Question 40Near-sighted (“myopic”) people require a corrective lens to restore normal vision. Thelens must bea) astigmatic;b) converging;c) diverging;a) presbyopic.Question 41The condition that two light waves interfere is that:a) they have the same wavelength;b) they have the same colour;c) they are “coherent” AND that they pass through the same region;a) none of the above.[Coherent means same frequency and fixed relative phase.]Question 42Three sources of light waves lie on the circumference of a circle and emit light in alldirections. Two are in phase and emit waves of equal amplitude. The third is 180 ◦ outof phase with the first two. Complete destructive interference occurs at the center ofthe circle:a) if the third source has twice the amplitude of each of the others;b) under no conditions;c) if all three sources have the same amplitude;a) if the third source has one half the amplitude of the other two.Question 43Blue light (λ = 450 nm) strikes a film of oil (n =1.5) with angle of incidence 0 ◦ . Theoil floats on water (n =1.33). What is the minimum thickness of the oil if the lightinterferes constructively?a) 75 nm;b) 150 nm;c) 112.5 nm;d) 225 nm.

Question 44In the diffraction pattern for a single slita) all fringes have the same intensity;b) the central fringe is the same width as all others;c) the wider the slit, the narrower the central fringe;a) the pattern is the same as that from a pair of slits.Question 45Two laser beams with, respectively, λ = 400 nm and λ = 600 nm are incident at rightangles to a diffraction grating. The m th order maximum for the 400 nm light is inexactly the same direction as the n th order for the 600 nm light. If the spacing in thediffraction grating is d, this means that 3n =2m.a) True;b) False.