Physics 112 Final
Estimate the most energetic X-ray you can get from a heavy atom with Z = 93. 118 keV 0.865 eV 164 MeV 5.19E7 eV None of these are good estimates.
118 keV WHY???
If the Bohr radius of the n = 3 state of a hydrogen atom is R, then the radius of the ground state is 9R. 3R. R/3. R/9. R.
R/9 (r sub n) = (n^2 r sub 1) (r sub 1) = R/3^2 = R/9
A square measuring 1 m by 1 m is moving away from Observer A along a direction parallel to one of the sides at a speed such that ϒ (defined above) is equal to 2. The area of the square measured by Observer A is 4 m^2. 2 m^2. 1 m^2. ½ m^2. ¼ m^2.
½ m^2 The size of the box wouldn't appear bigger to observer A if the box is moving away.
For the current to have its maximum value in a series RLC circuit... ω = 0 ω → ∞. (Angular frequency approaches infinity) ω = 1/(√LC) ω = (√LC) ω = 1/(√L/C)
ω = 1/(√LC) Maximum value occurs when impedance (Z) reaches min value. If L and C are equal, then Z will be at minimum. This equation is given by the text.
If a sinusoidal wave with intensity 10 W/m2 has an electric field of amplitude E, then a 20 W/m2 wave of the same wavelength will have an electric field of amplitude 4E. 2√2E. 2E. √2E. None of these.
√2E I = ½εocEmax^2 The sqrt of Emax at 10 W/m^2 means E The sqrt of 2Emax at 20 W/m^2 sqrt(2E)
How many 2d electron states can an atom have? 0 4 6 8 10
0 There is no 2d, only 3d 1s, 2s, 2p, 3s, 3p, 3d, 4s
A pair of narrow slits, separated by 1.8 mm, is illuminated by a monochromatic light source. Light waves arrive at the two slits in phase. A fringe pattern is observed on a screen 4.8 m from the slits. Monochromic light of wavelength 450 nm is used to illuminate the screen. The angular separation between adjacent fringes on the screen, measured in mrad, is closest to 0.15. 0.20. 0.25. 0.30. 0.36.
0.25 Angle of separation = wavelength/slit separation theta = lambda/d theta = (450 x 10^-9 m)/0.0018 m theta = 0.25
A series circuit has a 50-Hz AC source, a 60-ohm resistor, a 0.50-H inductor, and a 10-μF capacitor. The RMS current in the circuit is 2.2 A. The power factor of the circuit is closest to 0.35. 0.33. 0.31. 0.30. 0.28.
0.35 phi is the phase angle. cos phi is the power factor. R/Z is also the power factor. tan phi = (Xl-Xc)/R can find the phase angle. First convert inductor and capacitor to inductance and capacitance: Xl = wL = 314.16(0.5) = 157.08 Xc = 1/wC = 1/(314.16 x 10 x 10^-6) = 318.31 tan phi = (157.08 - 318.31)/60 = -2.687 cot -2.687 = phi phi = -69.59 cos -69.59 = 0.3487 = power factor
A lens of focal length 45 mm is used as a magnifier. The object being viewed is 6.8 mm long, and is positioned at the focal point of the lens. The lens is moved closer to the object, so that the image is now 25 cm from the lens. The distance the lens has been moved, in cm, is closest to 0.48. 0.55. 0.62. 0.69. 0.76.
0.69 1/f=1/a'-1/b 1/4.5 cm = 1/a' - 1/25 cm 0.26 = 1/a' a' = 3.846 a' = f - x 3.846 = 4.5 - x -x = -0.654 x = 0.654
A series ac circuit is shown below. The inductor has a reactance of 70 ohms and an inductance of 210 mH. A 30-ohm resistor and a capacitor whose reactance is 120 ohms are also in the circuit. The RMS current in the circuit is 2.0 A. The peak magnetic energy in the inductor is closest to 0.84 J. 0.42 J. 1.3 J. 1.7 J. 2.1 J.
0.84 J
An electron has a kinetic energy equal to twice its rest energy. The speed of the electron is closest to 0.84 c. 0.87 c. 0.89 c. 0.91 c. 0.94 c.
0.94 c. KE = (gamma - 1)mc^2 gamma = 3 3 = 1/sqrt(1-v^2/c^2) 9 = 1/(1-v^2/c^2) 1/9 = 1-v^2/c^2 v^2/c^2 = 8/9 v/c = 2sqrt(2)/3 v/c = 0.94
A 1.90 × 10^14 Hz (s^-1) electromagnetic wave propagates in carbon tetrachloride with a speed of 2.05 × 10^8 m/s. The wavelength of the wave in vacuum is closest to 1,580 nm. 1,080 nm. 1,260 nm. 1,420 nm. 1,740 nm.
1,580 nm c = lambda/f lambda = cf ***IN VACUUM*** which means the given wavelength is exchanged for 3x 10^8. Also, remember that Hz is s^-1 so the given frequency has to be in the denominator.
The inductor in a radio receiver carries a current of amplitude 200 mA when a voltage of amplitude 2.4 V is across it at a frequency of 1400 Hz. What is the value of the inductance? 1.43 mH 1.36 mH 9.20 mH 4.42 mH 1.97 mH
1.36 mH Inductance (Xl) means we are ONLY concerned with the inductor (L). V = iXl = iLw L = v/iw = v/i2pif L = 2.4 v / 2pi(1400Hzx0.2A) = 1.36 mH Omega (w) is equal to 2pi f
A tank holds a layer of oil, 1.43 m thick, which floats on a layer of syrup that is 0.64 m thick. Both liquids are clear and do not intermix. A ray, which originates at the bottom of the tank on a vertical axis, crosses the oil-syrup interface at a point 0.90 m from the axis. The ray continues and arrives at the oil-air interface, 2.00 m from the axis and at the critical angle. The index of refraction of the oil is closest to 1.64. 1.62. 1.66. 1.68. 1.70.
1.64 The displacement from the end point of the first ray is 1.1 m. Use COT (1.43/1.1) To find the critical angle at the surface of the water. Take the COS of the critical angle (52.43). Divide this INTO 1 (air index)
Unpolarized light with an original intensity Io passes through two ideal polarizers having their polarizing axes turned at 120° to each other. After passing through the polarizers, the intensity of the light is (√3/2) Io. 1/2 Io. (√3/4) Io. 1/4 Io. 1/8 Io.
1/8 Io (Io/2)cos^2 120 =(Io/2)(-1/2)^2 =(Io/2)(1/4) =Io/8
At most, how many bright fringes can be formed on one side of the central bright fringe (not counting the central bright fringe) when light of 625 nm falls on a double slit whose spacing is 6.77E-6 m? 8 9 10 11 12
10 6.77 x 10^-6 m/625 x 10^-9 = 10.8
The energy flow per unit time per unit area (S) of an electromagnetic wave has an average value of 695 mW/m^2. The wave is incident upon a rectangular area, 1.5 m by 2.0 m, at right angles. The total energy that traverses the area in a time interval of 1 min is closest to 260 J. 220 J. 190 J. 160 J. 130 J.
130 J Work = Power x Time Power = Intensity x Area W = AIT W = 0.695 W/m^2 x 1.5 m x 2 m x 60 s = 125.1 When in doubt, try to eliminate by units
A proton and an electron are 1.00 Å apart. (Å is the Ångstrom unit, which is 10^-10 m.) The potential energy of this pair of charges is closest to 14.4 J. 1.44 eV. 14.4 eV. 144 eV. 14.4 keV.
14.4 eV (8.99 x 10^9)x[(1.60 x 10^-19)^2]/1.0 x 10^-10 =2.30 x 10^-18 J = 14.4 eV
A light beam has a wavelength of 300 nm in a material of refractive index 1.5. In a material of refractive index 3.0 its wavelength will be 450 nm. 300 nm. 200 nm. 150 nm. 100 nm.
150 nm Index of refraction and wavelength are inversely proportionate
Consider an atom having the electron configuration 1s2 2s2 2p4 . The atom with the next higher Z and having similar chemical properties would have Z equal to 9. 15. 16. 34. 46.
16 You do not go OVER one because we are looking for similar chemical properties so you would go down the column to the element below. Z = 8 so you would want Z = 16 (sulfur)
An electron has the same de Broglie wavelength as a 390 nm photon. The speed of the electron is closest to 1,900 m/s. 2,100 m/s. 1,700m/s. 1,500 m/s. 540 m/s.
1900 m/s lambda = h/mv v = h/mlambda v = (6.626 x 10^-34)/(9.11 x 10^-31 * 390 X 10^-9) v = 1864.955
To the observer moving along with the square in Question 2 above, the time interval between consecutive blinks of her eyes is 1.0 s. To the stationary Observer A, this time interval is 2 s. 1 s. ½ s. ¼ s. ⅛ s.
2 s. Things seem slower when they are farther away.
A camera used for aerial surveillance has a lens with a 30-cm maximum aperture and a 42-cm focal length. Assume light of 550 nm wavelength is used and that the resolution of the camera is limited solely by diffraction. The angular resolution of the camera at maximum aperture, in µrad, is closest to 1.6. 2.2. 3.2. 4.5. 6.3.
2.2 sin(theta) = 1.22(lambda/diameter) 1.22(550 x 10^-9/0.3) = 2.4 x 10^-6 rad = 2.4 microrad
A lens of focal length 45 mm is mounted on a 35-mm camera. The lens aperture is set at f/2 and the shutter speed set at 1/2000 s. The aperture diameter, in mm, is closest to 16. 19. 23. 26. 29.
23 f-number= focal length/aperture diameter D = f/f# D = 45/2 D = 22.5
A ray in glass is incident onto a water-glass interface, at an angle of incidence equal to half the critical angle for that interface. The indices of refraction for water and the glass are 1.33 and 1.43, respectively. The angle that the refracted ray in the water makes with the normal is closest to 47°. 42°. 37°. 32°. 27°.
37° The angle of the refracted ray is equal to the angle of incidence. The critical angle is found by sin theta = nb/na
A double convex thin glass lens has equal radii of curvature. The focal length of the lens is +37.3 cm, and the index of refraction of the glass is 1.52. The radius of curvature of each convex surface, in cm, is closest to 31. 35. 39. 43. 46.
39 1/f = (n-1)(2/R). 1/37.3 = (1.52-1)(2/R) 0.268 = 0.52(2/R) 0.0516 = 2/R R = 2/0.0516 = 38.76
A laser pulse of duration 25 ms has a total energy of 1.4 J. If the wavelength of this radiation is 567 nm, how many photons are emitted in one pulse? 1.6E17 3.2E17 4.0E18 4.8E19 9.9E17
4.0E18 f = c/lambda f = 3.0 x 10^8/567 x 10^-9 f = 5.29 x 10^14 s^-1 E = hf E = (6.626 x 10^-34)(5.29 x 10^14) E = 3.5 x 10^-19 J / 1.6 x 10^-19 J 2.19 eV 1.4 J/1.6 x 10^-19 = 8.75 x 10^18 8.75 x 10^18/2.19 = 4.0 x 10^18
An 18-mm-wide diffraction grating has rulings of 710 lines per mm. Light is incident normally on the grating. Monochromatic light of 506 nm wavelength is used. The largest angle from the normal at which an intensity maximum is formed is closest to 38°. 42°. 40°. 44°. 46°.
46° FIRST find order... m = d/lambda = 2 Plug in to dsin(theta) = lambdaxm sin(theta) = (506 x 10^-6)(2)/(0.0014) sin(theta) = 0.72 inverse sin (0.72) = 46.05 theta = 46.05
The work function of a particular substance is 4.2E-19 J. What is the photoelectric cutoff wavelength for this material? 308 nm 393 nm 473 nm 554 nm None of these.
473 nm lambda = hc/E lambda = plancks constant x speed of light/given energy = 473 nm
The spacing of ruled lines on a diffraction grating is 1770 nm. The grating is illuminated at normal incidence with a parallel beam of white light in the 400 nm to 700 nm wavelength band. The longest wavelength that appears in the third order spectrum is closest to 530 nm. 550 nm. 570 nm. 590 nm. 610 nm.
590 nm. Use the dsin(theta) = lambdaxm equation. Sin(theta) = 1 because its a maximum. The equation becomes d = lambdaxm 1770 nm = 3lambda lambda = 590 nm
A pair of narrow slits, separated by 1.8 mm, is illuminated by a monochromatic light source. Light waves arrive at the two slits in phase. A fringe pattern is observed on a screen 4.8 m from the slits. If there are 5.0 bright fringes/cm on the screen, the wavelength of the monochromic light is closest to: 550 nm. 600 nm. 650 nm. 700 nm. 750 nm.
750 nm y = R(m lambda/d) 1 = 4.8(5 lambda/1.8) 1.8/4.8 = 5 lambda lambda = 0.375/5 lambda = 0.075
A series ac circuit is shown below. The inductor has a reactance of 50 ohms and an inductance of 240 mH. A 50-ohm resistor and a capacitor whose reactance is 140 ohms are also in the circuit. The RMS current in the circuit is 1.2 A. The capacitor is changed so that the circuit is in resonance. The voltage of the source is adjusted so that the RMS current of 1.2 A is maintained. The new voltage amplitude of the source is closest to 85 V. 73 V. 61 V. 97 V. 110 V.
85 V
A circuit has a resistance of 4.0Ω; a reactance, due to the capacitance, of 26Ω; and a reactance, due to the inductance, of 17Ω. Find the impedance of the circuit. 9.8 Ω 31 Ω 13 Ω 47 Ω 67 Ω
9.8 Ω Use impedance (Z) equation, plug in numbers, and solve.
A slide projector produces a real erect image of the slide. a virtual erect image of the slide. a real inverted image of the slide. a virtual inverted image of the slide. none of the above.
A real inverted image of the slide. Slides are upside down images. The projector lens flips it so that the projected image is upright to the human eye.
Part of the energy level diagram of a certain atom is below. The energy spacing between Levels 1 and 2 is twice what is between Levels 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 between the three energy levels? Both λ/2 and λ/3 Only λ/2 Both 2λ and 3λ Only 2λ None of these wavelengths can be produced.
Both λ/2 and λ/3 WHY?
As you move an object from just outside to just inside the focal point of a converging lens, its image goes from real to virtual and from inverted to erect. goes from inverted to erect but remains real. goes from inverted to erect but remains virtual. goes from real to virtual but remains inverted. remains both erect and virtual.
Goes from real to virtual and from inverted to erect. Images inside the focal point on a converging lens are virtual. Virtual images are erect.
Consider a hypothetical single-electron Bohr atom for which an electron in the n = 1 shell has a total energy of -81.0 eV. An electron in the n = 3 shell has a total energy of -9.00 eV. Which of the statements below is/are accurate? The energy needed to ionize the atom is 90.0 eV. It takes 90.0 eV to move an electron from the n =1 to the n = 3 shell. If an electron makes a transition from the n = 3 to the n = 1 shell, it will give up 72.0 eV of energy. If an electron makes a transition from the n = 3 to the n = 1 shell, it must absorb 72.0 eV of energy. More than one of the above statements are accurate.
If an electron makes a transition from the n3 to the n1 shell it will give up 72 eV of energy. -9 -? = -81 -81 + 9 = -72 - means giving up
When light travels from air into water, -its velocity, wavelength, and frequency all change. -its velocity changes, but its frequency and wavelength do not change. -its frequency changes, but its velocity and wavelength do not change. -its velocity and wavelength change, but its frequency does not change. -its wavelength changes, but its velocity and frequency do not change.
Its velocity and wavelength change, but its frequency does not change. Index of refraction is dependent on speed. It is defined by speed in a material and speed in a vacuum. Wavelength can change since speed changes, however frequency remains the same in any material.
Which of the following is NOT a characteristic of laser light? All the photons in laser light are in phase with each other. Laser light contains a very broad spectrum of wavelengths. The photons produced by a laser all travel in the same direction. The photons in laser light all have the same frequency. All of the statements above represent characteristics of laser light.
Laser light contains a very broad spectrum of wavelengths. The laser has only the wavelength for the specific color of light. Ex a red laser and green laser have different wavelengths, not a broad spectrum
A thin glass lens has a focal length f in air. If you now make a lens of identical shape, using glass having twice the refractive index of the original glass, what is the focal length of the new lens? f/2 Less than f/2 2f Greater than f/2 The focal length does not change.
Less than f/2 The increased refractive index causes light to bend more and decreases the focal length by the same quantity. It is LESS than 2 because the refractive index of air is >0 and has to be considered.
If without changing anything else, you double the focal length of both of the lenses in a refracting telescope with an original angular magnification M, what is the new magnification? 4M 2M M M/2 M/4
M M = y'f2/y'f1 The doubled focal points cancel each other out.
Light of wavelength λ and frequency f passes through a single slit of width a. The diffraction pattern is observed on a screen a distance x away from the slit. Which of the following will decrease the width of the central maximum? Decrease the slit width Decrease the frequency of the light Decrease the wavelength of the light Decrease the distance x of the screen from the slit. More than one of the above actions will cause the width to decrease.
More than one of the above actions will cause the width to decrease. decrease the distance x of the screen from the slit, decrease wavelength slit width and light width are inverse
A rocket is traveling at (1/3)c relative to Earth when a lightbulb in the center of a cubical room is suddenly turned on. An astronaut at rest in the rocket and a person at rest on Earth both observe the light hit opposite walls of the room. Call these Events A and B. Which statement (statements) is (are) accurate concerning the observation? To the observer on Earth, both events happen at the same time. To the astronaut in the rocket, both events happen at the same time. To the observer on Earth, Event B happens before Event A. To the astronaut in the rocket, Event A happens after Event B. More than one of the above statements are accurate.
More than one of the above statements are accurate. To the observer on earth, both events happen at the same time, to the astronaut in the rocket, event a happens after event b.
An object lies outside the focal point of a converging lens. Which of the following statements concerning the image formed by the lens is accurate? The image is always real and inverted. The image could be real or virtual, depending on how far the object is past the focal point. The image could be erect or inverted, depending on how far the object is past the focal point. The image is always on the opposite side of the lens from the object. More than one of the statements above are accurate.
More than one of the statements above are accurate The image is always real and inverted. The image is always on the opposite side of the lens from the object.
Which of the following statements is/are accurate concerning a compound microscope? The objective lens produces an inverted virtual image of the object. The image produced by the objective lens is just inside the focal point of the eyepiece. The final image is inverted compared with the original object. The object to be viewed is placed just inside the focal point of the objective lens. More than one of the statements above are accurate.
More than one of the statements above are accurate. The image produced by the objective lens is just inside the focal point of the eyepiece The final image is inverted compared with the original object
Two lasers each produce 2 mW beams. The beam of laser B is wider, having twice the cross-sectional area as the beam of laser A. Which of the following statements concerning the beams is (are) accurate? Both of the beams have the same average power. Beam A has twice the intensity of beam B. Beam B has twice the intensity of beam A. Both of the beams have the same intensity. More than one of the statements above is accurate.
More than one of the statements above is accurate. They should have the same intensity and power
An atom having the electron configuration 1s2 2s2 2p6 3s2 3p5 has 17 orbital electrons. 11 orbital electrons. Electrons with l = 0, 1, 2. Electrons with m = 0 and ± 1. More than one of these is accurate.
More than one of these is accurate. 17 orbital electrons, electrons with m = 0 and +/- 1
An electron on the N shell can have which of the following quantum numbers? s = -½ ml = -3 ml = 4 n = -4 More than one of these is possible.
More than one of these is possible. m = -3, s = -1/2 M can't exceed -3/3, n goes up to 4, l goes up to 3, spin (s) can take on 1/2 or -1/2
If you were in a spaceship traveling at a speed close to the speed of light (with respect to Earth) you would notice that some of your physical dimensions were smaller than normal. your mass is different than normal. your pulse rate is different than normal. none of these effects occur. more than one of these effects occur.
None of these effects occur. Travel at the speed of light wouldn't have an affect on any of these. Time and size are relative, but only to outsiders.
A series R-L-C circuit with a sinusoidal voltage source of angular frequency omega has a total reactance X. If the frequency is doubled, the reactance becomes... (X/2, X/4, 2X, 4X, none)
None of these. Xc reactance becomes X/2 and Xl becomes 2X so in total they remain 1X.
A series RLC circuit has a sinusoidal voltage source of angular frequency omega. If the frequency is doubled... The inductive reactance is doubled The capacitive reactance is doubled The total reactance is doubled The impedance is doubled The current is doubled
The inductive reactance is doubled. The capacitive reactance would HALVE. None of the other statements are correct. We saw in the previous question why the total reactance remains at 1X. Impedance and current are not directly enough related here.
A camera is focusing on an animal. As the animal moves closer to the lens, what must be done to keep the animal in focus? The lens must be moved closer to the film (or light sensors for a digital camera). The lens must be moved farther from the film (or light sensors for a digital camera). The f-number of the lens must be increased. The f-number of the lens must be decreased. More than one of the above is necessary for the animal to remain focus
The lens must be moved farther from the film (or light sensors for a digital camera) F-number isn't important for focusing.
Light falling on a metal surface causes electrons to be emitted from the metal by the photoelectric effect. As the frequency of the light increases (everything else remains the same), which of the following statements is accurate? The number of electrons emitted from the metal increases. The maximum speed of the emitted electrons increases. The maximum speed of the emitted electrons does not change. The work function of the metal increases. More than one of the above statements is accurate.
The maximum speed of the emitted electrons increases. The photoelectric effect supports this. Energy from outside source excites electrons to move faster.
In a series R-L-C circuit at resonance... The impedance is zero The impedance has its maximum value The reactance is equal to R. The total impedance has its minimum value, which is equal to R None of these
The total impedance has its minimum value, which is equal to R. At resonance Xl and Xc are equal. As we saw before, when these are equal impedance is at a minimum
What is the essential difference between microwaves and blue light? One has an electric charge, and the other does not. One undergoes refraction, and the other does not. One is a form of radiation, and the other is not. Blue light is a beam of photons. Microwaves are not photons. There is no essential difference in the nature of microwaves and blue light other than a difference in frequency and wavelength
There is no essential difference in the nature of microwaves and blue light other than a difference in frequency and wavelength They are both light waves. The only difference will be frequency due to type of wave and wavelength due color
Which of the following statements is/are accurate concerning the lenses used in eyeglasses to correct nearsightedness and farsightedness? They produce a real image. They produce a virtual image. Both nearsightedness and farsightedness are corrected with a converging lens. Both nearsightedness and farsightedness are corrected with a diverging lens. More than one of the statements above are accurate.
They produce a real image. They are NOT both corrected by the same type of lens. Nearsighted = diverging Farsighted = converging
Consider an atom with the electron configuration 1s2 2s2 2p6 3s2 3p6. Which of the following is an accurate statement concerning this atom? The atomic number of this atom is Z = 11. This atom is in an excited state. This atom has a non-zero angular momentum. This atom is most likely to give rise to an ion with charge +2e. This atom would probably be very inert chemically.
This atom would probably be very inert chemically. This is a noble gas. All electron levels are full.
You have a shiny salad bowl with a spherical shape. If you hold the bowl at arm's length with the inside of the bowl facing you, the image of your face that you see will be upside down and smaller than your face. right side up and smaller than your face. right side up and bigger than your face. Upside down and bigger than your face. The image is behind the bowl so you will not see it.
Upside down and smaller than your face. It is outside of the focal point so it is upside down. It's smaller than your face because the rays converge into the image closer to the focal point. The closer you hold it to your face the bigger the image will be.
Which of the phasor diagrams shown below represents a series RLC circuit driven at resonance?
Vl and Vc should be the same length and pointing in EXACTLY the opposite direction with Vr directly perpendicular to the line formed by Vl and Vc
An oil film (n = 1.48) of thickness 290 nm floating on water is illuminated with white light at normal incidence. What is the wavelength of the dominant color in the reflected light? Green (541 nm) Blue-green (493 nm) Violet (404 nm) Yellow (572 nm) Blue (470 nm)
Yellow (572 nm) (2d)n = (2m + 1)lambda/2 2(290)1.48 = 3lambda/2 4(290)1.48 = 3lambda 1716.8 = 3lambda lambda = 572.27
