Young Double Slit Experiment - Physics - Exam Paper, Exams of Physics

Download Young Double Slit Experiment - Physics - Exam Paper and more Exams Physics in PDF only on Docsity! Canadian Association of Physicists 2001 Prize Exam This is a three hour exam. National ranking and prizes will be based on a student’s performance on both sections A and B of the exam. However, performance on the multiple choice questions in part A will be used to determine whose written work in part B will be marked for prize consideration by the National Committee. The questions in part B of the exam have a range of difficulty. Please be careful to gather as many of the easier marks as possible before venturing into more difficult territory. If an answer to part (a) of a question is needed for part (b), and you are not able to solve part (a), assume a likely solution and attempt the rest of the question anyway. No student is expected to complete this exam and parts of each problem may be very challenging. Non-programmable calculators may be used. Please be very careful to answer the multiple choice ques- tions on the answer card/sheet provided; most im- portantly, write your solutions to the three written problems on separate sheets as they will be marked by people in different parts of Canada. Good luck. Data Speed of light c = 3.00× 108 m/s Gravitational constant G = 6.67× 10−11 N·m2/kg2 Acceleration due to gravity g = 9.80 m/s2 Fundamental charge e = 1.60× 10−19 C Mass of electron me = 9.11× 10−31 kg Mass of proton mp = 1.673× 10−27 kg Planck’s constant h = 6.63× 10−34 J·s Coulomb’s constant 1/4πo = 8.99× 109 J·m/C2 Permeability of free space µo = 4π × 10−7 N/A2 Speed of sound in air vs = 343 m/s Density of air ρ = 1.2 kg/m3 Boltzmann constant k = 1.38× 10−23 J/K Energy Conversion 1 eV=1.6× 10−19 J Avogadro’s number NA = 6.02× 1023 mol−1 Part A: Multiple Choice Question 1 Three identical resistors are connected across a voltage source V so that one of them is in parallel with two others which are connected in series. The power dissipated through the first one, compared to the power dissipated by each of the other two, is approximately (a) the same. (b) half as much. (c) twice as much. (d) four times as much. Question 2 The diagram below shows various positions of a child in motion on a swing. Somewhere in front of the child a station- ary whistle is blowing. At which position will the child hear the highest frequency for the sound of the whistle? A B C D
whistle (a) At B when moving toward A. (b) At B when moving toward C. (c) At C when moving toward B. (d) At C when moving toward D. Question 3 In a Young double slit experiment, green light is incident on the two slits. The interference pattern is observed on a screen. Which one of the following changes would cause the observed fringes to be more closely spaced? screen incoming light w
aves fringes (a) Reducing the separation between the slits. (b) Using blue light instead of green light. (c) Using red light instead of green light. (d) Moving the light source further away from the slits. Question 4 A thin lens with focal length f is to be used as a magnify- ing glass. Which of the following statements regarding this situation is true? (a) A converging lens must be used, and the object be placed at a distance greater than 2f from the lens. (b) A diverging lens must be used, and the object be placed between f and 2f from the lens. (c) A converging lens must be used, and the object be placed at a distance less than f from the lens. (d) A diverging lens must be used, and the object be placed at any point other than the focal point. Canadian Association of Physicists Prize Exam 2001 Question 5 The figure shows the path of a ray of light as it passes through three different materials with refractive indices n1, n2 and n3. The figure is drawn to scale. What can we con- clude concerning the indices of these three materials? n1 n2 n3 (a) n3 < n2 < n1. (b) n3 < n1 < n2. (c) n2 < n1 < n3. (d) n1 < n3 < n2. Question 6 The diagram shows the trajectory of three artillery shells. Each was fired with the same initial speed. Which shell was in the air for the longest time? (Ignore air friction.) A B C
(a) Shell A. (b) Shell B. (c) Shell C. (d) Shells A and C were in the air for equal time, which was longer than for shell B. Question 7 Let V be electric potential andE the magnitude of the elec- tric field. At a given position, which of the following state- ments is true? (a) E is always zero where V is zero. (b) V is always zero where E is zero. (c) E can be zero where V is nonzero. (d) E is always nonzero where V is nonzero. Question 8 Two test charges are brought successively to a position some distance away from a negative charge −Q. First, test- charge q is placed at a distance R from −Q. Then it is re- moved and a test-charge −2q is placed at a distance 2R from −Q. The sign of q is unknown. Compared with the electric potential at the position of the test-charge in the first case, the electric potential at the position of the second test-charge is R 2R – Q q – 2q– Q (a) (b) (a) the same. (b) twice as large. (c) half as large. (d) impossible to determine unless the sign of q is known. Question 9 A simple pendulum, consisting of a mass m at the end of an unstretchable string of length L, swings upward, making an angle θ with the vertical. The work done by the tension in the string is (a) Zero. (b) mgL (c) mgL cos θ (d) -mgL sin θ Question 10 In problems involving electromagnetism it is often conve- nient and informative to express answers in terms of a con- stant, α, which is a combination of the Coulomb constant, ke = 1/4π0, the charge of the electron, e, and h̄ = h/2π, h being Planck’s constant. For instance, the lowest energy that a hydrogen atom can have is given by E = − 12α 2mc2, where m is the mass of the electron and c is the speed of light. Which of the following is the correct expression for α? (HINT: non-relativistic kinetic energy is 12mv 2, where v is speed.) (a) kee 2 h̄c . (c) kee 2h̄ c . (b) h̄ kee2c . (d) kee 2c h̄ 2