Wavelength of Yellow Light - Physics - Past Paper, Exams of Physics

Download Wavelength of Yellow Light - Physics - Past Paper and more Exams Physics in PDF only on Docsity! Physics 152 Roster No.: November 19, 2004 Score: Midterm Exam #3, Part A Exam time limit: 50 minutes. You may use a calculator and both sides of TWO sheets of notes, handwritten only. Closed book; no collaboration. For multiple choice questions, circle the letter of the one best answer (unless more than one answer is asked for). Ignore gravity in all problems unless told otherwise, and ignore relativistic effects in non-relativistic problems. c = 2.998 × 108 m/s 1. (3 pts.) TRUE or FALSE (T or F) for EM waves in empty space (vacuum): ______ Orange light has lower frequency than blue light. ______ Infrared light has longer wavelengths than ultraviolet light. ______ Microwaves have shorter wavelengths than x-rays. ______ Ultraviolet light travels faster than violet light. ______ Electromagnetic waves are transverse waves. ______ Radio waves, microwaves, and light are electromagnetic waves, but x-rays and gamma rays are not. 2. Crystal-ball gazing is one of the wizarding skills that Harry Potter is taught at Hogwarts School. a. (1 pt.) Suppose that Harry accidentally looks all the way through the crystal ball at real-life objects on the other side of the ball. Which kind of lens will the crystal ball function as? (Hint: Think about the curvature of opposite sides of the ball. Which sort of lens does that remind you of?) A. converging B. diverging b. (2 pts.) Some lit candles are on the far side of the room, a very long distance from the crystal ball. When Harry looks at them through the center of the crystal ball, how will their image appear? A. upright and real C. inverted and real B. upright and virtual D. inverted and virtual c. (2 pts.) A book of spells is just on the other side of the crystal ball from Harry, almost touching the crystal ball. When Harry reads the spells through the center of the crystal ball, he sees that the image is enlarged (magnified). The image is also: A. upright and real C. inverted and real B. upright and virtual D. inverted and virtual 3. You hold a circular soap film (from a bubble-blowing kit) vertically, causing the film to drain a bit downwards: the upper edge of the soap film becomes vanishingly thin, and the lower edge becomes thicker. When you illuminate it perpendicularly with monochromatic yellow light (λ = 589 nm in air) and you look at the light reflected directly back from the soap film (i.e., you are positioned on the same side of the film as the light source), you see a pattern of bright and dark fringes. You are told: nfilm = 1.33 and nair = 1.00. a. (2 pts.) The wavelength of the yellow light inside the soap film is: A. 295 nm D. 503 nm B. 443 nm E. 556 nm C. 471 nm F. 589 nm (the same as in air) b. (1 pt.) At the top of the film, where its thickness is very nearly zero, would you expect to see reflected a bright or dark fringe? A. bright B. dark c. (2 pts.) If you count a total of 12 bright fringes from the top to the bottom of the soap film, approximately how thick is the soap film near the bottom? (Hint: Without worrying about every detail, just estimate a rough answer, and choose the closest answer choice.) A. 2.6 nm D. 2.6 µm B. 26 nm E. 260 µm C. 260 nm F. 2.6 mm 4. When the Sun is moderately low in the sky, you see sunlight reflected from the surface of nearby water puddles. Light reflected an angle near Brewster’s angle is almost entirely horizontally polarized. a. (1 pt.) You hold up a polarizer so that the reflected light passes through it before reaching your eyes. If the reflected light is indeed horizontally polarized, then which of the following will be TRUE? Choose one: A. When the polarizer’s axis is horizontal, none of the reflected light is allowed through the polarizer. B. When the polarizer’s axis is horizontal, all of the reflected light is allowed through the polarizer. C. When the polarizer’s axis is vertical, none of the reflected light is allowed through the polarizer. D. When the polarizer’s axis is vertical, all of the reflected light is allowed through the polarizer. E. both A and D F. both B and C b. (2 pts.) If you turn the polarizer so that its polarization axis is tilted at an angle of 30.˚ to the horizontal, what fraction of the above light’s intensity will pass through the polarizer? A. 50.% D. 67% B. 57% E. 72% C. 60.% F. 75% c. (1 pt.) Suppose that a different light ray traveling parallel to the ground also happens to be horizontally polarized. The light has which of the following properties? Choose one: A. an electric field that is horizontal B. an electric field that is vertical C. a magnetic field that is horizontal D. a magnetic field that is vertical E. both A and D F. both B and C