PHY 1223 Electricity & Light Final Exam Fall 2023 PDF

PH-UY 1223: ELECTRICITY & LIGHT FINAL EXAM Name 12/20/23 NetID On the exam, blue book, and answer sheet, write: BEFORE YOU START… your FULL name (as listed by the university...

PH-UY 1223: ELECTRICITY & LIGHT FINAL EXAM Name 12/20/23 NetID On the exam, blue book, and answer sheet, write: BEFORE YOU START… your FULL name (as listed by the university registrar) your NetID (i.e. your NYU email minus “@nyu.edu”) 1. Two point charges of 5 nC each are located at two of the corners of an equilateral triangle with sides of length 50 cm. What is the magnitude of the electric field at the third corner of the triangle? a) 286 N/C b) 498 N/C c) 374 N/C d) 436 N/C e) 311 N/C 2. An electron is moving in a circular path perpendicular to a magnetic field with magnitude 35 mT. If the radius of the circular path is 0.3 mm, what is the speed of the electron? Use 9.1 x 10-31 kg for the mass of an electron. a) 3.08 x 106 m/s b) 3.69 x 106 m/s c) 1.85 x 106 m/s d) 1.98 x 106 m/s e) 2.46 x 106 m/s 3. If a 12 volt battery is connected to five resistors (100 Ω each) all in parallel, what is the power dissipated in each resistor? a) 1.44 W b) 1.67 W c) 0.640 W d) 0.810 W e) 1.21 W 4. If the intensity of a laser beam is 600 W/m2, what is the root mean square value for the electric field in the path of the beam? Recall that the root mean square value for the electric field is the amplitude of the electric field wave divided by the square root of 2. a) 514 N/C b) 476 N/C c) 621 N/C d) 549 N/C e) 434 N/C 5. A certain type of glass has an index of refraction of 1.55. What is the critical angle for light in this glass when it is surrounded by water? Use 1.33 for the index of refraction of water. a) 62.5° b) 56.2° c) 53.7° d) 59.1° e) 51.1° 6. The speed of light in a certain type of glass is 2.4 x 108 m/s. If light in air is incident on this glass at an angle of 32°, what will be the angle of refraction? a) 25.1° b) 27.3° c) 22.9° d) 20.7° e) 34.4° 7. When a 4 cm tall object is placed 30 cm in front of a convex spherical mirror that has a radius of curvature with magnitude 50 cm, how tall is the image? a) 1.33 cm b) 1.82 cm c) 2.00 cm d) 1.67 cm e) 1.54 cm 8. When an object is placed in front of a concave spherical mirror that has a radius of curvature of 40 cm, the image is upside down and just as tall as the object. How far is the object from the mirror? Hint: In this case, the image and the object are at the same distance from the mirror. a) 30 cm b) 60 cm c) 70 cm d) 40 cm e) 50 cm 9. A diverging lens has two concave surfaces, one with radius of curvature with magnitude of 30 cm, and the other with magnitude 20 cm. If the focal length of the lens is -22 cm, what is the index of refraction of the glass? a) 1.60 b) 1.40 c) 1.46 d) 1.50 e) 1.55 10. Two converging lenses, each with focal length 30 cm are placed 20 cm apart. If an object is placed 10 cm in front of the first lens, how far behind the second lens will the final image appear? a) 99.5 cm b) 81.2 cm c) 210 cm d) 67.1 cm e) 51.5 cm  PH-UY 1223: ELECTRICITY & LIGHT 11. When a soap bubble has a thickness of 125 nm, what wavelength of normally incident visible light will be most strongly reflected? Use 1.33 for the index of refraction of the soapy water. a) 505 nm b) 665 nm c) 412 nm d) 612 nm e) 452 nm 12. When light with wavelength of 670 nm is normally incident on a single slit, the width of the central diffraction peak on a screen 2.5 m away is 5 cm. What will be the width of the central diffraction peak on the screen if instead the incoming light has a wavelength of 440 nm? a) 3.66 cm b) 3.81 cm c) 3.28 cm d) 3.22 cm e) 3.51 cm 13. When a laser beam with wavelength of 633 nm is incident on a diffraction grating on a spectroscope, the second order line is measured to be deflected at an angle of 56°. How many lines per centimeter are there on the grating? a) 5870 b) 5110 c) 6220 d) 5490 e) 6550 14. When light traveling in air is incident on the surface of a liquid that has an index of refraction of 1.25, the reflected beam is observed to be completely polarized. What is the angle of incidence? a) 51.3° b) 57.2° c) 55.4° d) 53.5° e) 49.2° 15. Two craters on the moon are 5 km apart. To resolve them from the earth with a telescope, what minimum diameter lens would you need? The distance from the earth to the moon is 3.84 x 108 m. Use 550 nm for the wavelength of the light. a) 6.44 cm b) 4.29 cm c) 3.68 cm d) 7.51 cm e) 5.15 cm  Equation Sheet for Ph1223 N.m2 µ0 ∆l ~ × r̂ k = 8.99 × 109 ~ B = I C2 4π r2 C2 µ0 I 0 = 8.85 × 10−12 B = N.m2 2R −19 µ0 I e = 1.6 × 10 C B = µ0 = 4π × 10−7 H/m 2πR B = µ0 nI c = 3.00 × 108 m/s F µ0 I1 I2 1 = k = l 2πr 4π0 ~ ·A ~ ΦB = B v = v0 + at 1 ∆φB x = x0 + v0 t + at2 E = −N 2 ∆t E = vBl v2 = v02 + 2a(x − x0 ) kq1 q2 L = µ0 n2 Al F~2,1 = 2 r̂1,2 c = fλ r1,2 E = cB ~ F~ P E = I = q A ~ kq E0 B0 E = r̂ I = r2 2µ0 ~ λ 2kλ θi = θr E = r̂ = r̂ 2π0 r r σ n1 sin θ1 = n2 sin θ2 E = = 2πkσ 1 1 1 20 + = ~ · ∆r ~ do di f ∆V = −E R kQ f = V = 2 r di ∆P E = Q∆V M = − do Q = C∆V   1 1 1 Q2 1 = (n − 1) + U = = C∆V 2 f R1 R2 2C 2 1 A P = C = 0 (for parallel plate) f d c Ceq = C1 + C2 +... v = n 1 1 1 λ0 = + +... λ = Ceq C1 C2 n I = nqvd A d sin θ = mλ I y J = = σE d = mλ A L   V = IR 1 λ0 2t = m+ L 2 n R = ρ A λ0 P = I 2R 2t = m n Req = R1 + R2 +... D sin θ = mλ y 1 1 1 D = mλ = + +... L Req R1 R2 I = I0 cos2 θ F~ = ~ q~v × B n2 tan θP = F~ = I~l × B ~ n1 qB y λ f = ≈ 1.22 2πm L D ~ µ0 ~v × r̂ B = q 4π r2 1