Review Session 1. Dr. Flera Rizatdinova

Transcription

1 Review Session 1 Dr. Flera Rizatdinova

2 Summary of Chapter 23 Index of refraction: Angle of reflection equals angle of incidence Plane mirror: image is virtual, upright, and the same size as the object Spherical mirror can be concave or convex Focal length of the mirror: 2014 Pearson Education, Inc.

3 Summary of Chapter 23 Mirror equation: Magnification: Real image: light passes through it Virtual image: light does not pass through 2014 Pearson Education, Inc.

4 Summary of Chapter 23 Law of refraction (Snell s law): Total internal reflection occurs when angle of incidence is greater than critical angle: A converging lens focuses incoming parallel rays to a point A diverging lens spreads incoming rays so that they appear to come from a point 2014 Pearson Education, Inc.

5 Summary of Chapter 23 Power of a lens: Thin lens equation: Magnification: 2014 Pearson Education, Inc.

6 Multiple Choice Q1 An object is in front of a concave spherical mirror, and its image is 4.0 cm behind the mirror. If the focal length of the mirror has a magnitude of 5.0 cm, where is the object? A) 2.2 cm in front of the mirror B) 2.2 cm behind the mirror C) 9.0 cm in front of the mirror D) 1.0 cm behind the mirror Answer: A

7 MC Q2 A wrench is placed at 30 cm in front of a diverging lens with a focal length of magnitude 10 cm. What is the magnification of the wrench? A) 0.25 B) C) 0.67 D) E) 4.0 Answer: A

8 Problem 1 A beam of light in air strikes a slab of glass (n = 1.51) and is partially reflected and partially refracted. Determine the angle of incidence if the angle of reflection is twice the angle of refraction. Answer: 81.9

9 Problem 2 An object is placed 9.5 cm in front of a convex lens with a focal length of magnitude 24 cm. (a) Where is the image formed and how far is it from the lens? (b) What is the magnification produced by the lens? Answer: (a) 16 cm in front of the lens (b) 1.7

10 Problem 3 A bright object and a viewing screen are separated by a distance of 86.0 cm. At what location(s) between the object and the screen should a lens of focal length 16.0 cm be placed in order to produce a sharp image on the screen? Answer: do=64.7cm and do =21.3 cm

11 Summary of Chapter 24 Wavelength of light in a medium with index of refraction n: In the double-slit experiment, constructive interference occurs when and destructive interference when 2014 Pearson Education, Inc.

12 Summary of Chapter 24 Light bends around obstacles and openings in its path, yielding diffraction patterns Light passing through a narrow slit will produce a central bright maximum of width: The intensity of plane polarized light is reduced after it passes through another polarizer: 2014 Pearson Education, Inc.

13 MC Q3 Blue light of wavelength λpasses through a single slit of width d and forms a diffraction pattern on a screen. If we replace the blue light by red light of wavelength 2λ, we can retain the original diffraction pattern if we change the slit width (a) to d/4. (b) to d/2. (c) not at all. (d) to 2d. (e) to 4d. Answer: D 2014 Pearson Education, Inc.

14 Problem 4 Light of wavelength 470 nm in air shines on two slits mm apart. The slits are immersed in water, as is a viewing screen 40.0 cm away. How far apart are the fringes on the screen? Answer: m 2014 Pearson Education, Inc.

15 Problem 5 When yellow sodium light, λ= 589 nm, falls on a diffraction grating, its first-order peak on a screen 72.0 cm away falls 3.32 cm from the central peak. Another source produces a line 3.71 cm from the central peak. What is its wavelength? How many slits/cm are on the grating? Answer: 658 nm; 782 lines/cm 2014 Pearson Education, Inc.

16 Problem 6 Two polarizers are oriented at 48 to each other and plane-polarized light is incident on them. If only 35% of the light gets through both of them, what was the initial polarization direction of the incident light? I 1 = I 0 cos 2 θ 1 ; I 2 = I 1 cos 2 θ 2 = I 0 cos 2 θ 1 cos 2 θ 2 = 0.35I 0 # θ 1 = cos & # % $ cosθ ( = 0.35 & cos 1 % 2 ' $ cos 48 ( = 28 '

17 Problem 7 Four polarizers are placed in succession with their axes vertical, at 30.0 to the vertical, at 60.0 to the vertical, and at 90.0 to the vertical. (a) Calculate what fraction of the incident unpolarized light is transmitted by the four polarizers. (b) Can the transmitted light be decreased by removing one of the polarizers? If so, which one? (c) Can the transmitted light intensity be extinguished by removing polarizers? If so, which one(s)? I 1 = 1 2 I 0 ; I 2 = I 1 cos2 θ 2 = 1 2 I 0 cos2 θ 2 ; I 3 = I 2 cos 2 θ 3 = 1 2 I 0 cos2 θ 2 cos 2 θ 3 ; I 4 = I 3 cos 2 θ 4 = 1 2 I 0 cos2 θ 2 cos 2 θ 3 cos 2 θ 4 = 1 2 I 0 cos cos cos = 0.211I 0

18 Cont d If the second polarizer is removed, then the angle between polarizers 1 and 3 is now I 1 = 1 2 I 0 ; I 3 = I 1 cos2 θ 3 = 1 2 I 0 cos2 θ 3 ; I 4 = I 3 cos 2 θ 4 = 1 2 I 0 cos2 θ 3 cos 2 θ 4 = 1 2 I 0 cos cos = I 0 The same value would result by removing the third polarizer, because then the angle between polarizers 2 and 4 would be The intensity can be decreased by removing either the second or third polarizer. If both the second and third polarizers are removed, then there are still two polarizers with their axes perpendicular, so no light will be transmitted.

19 Summary of Chapter 25 Simple magnifier: object at focal point Angular modification: Astronomical telescope: objective and eyepiece; object infinitely far away Telescope magnification: 2014 Pearson Education, Inc.

20 Summary of Chapter 25 Compound microscope magnification:! M = # N " f e $! & l f e # %" d o $ & % Resolution of optical devices is limited by diffraction θ = 1.22λ D 2014 Pearson Education, Inc.

21 Problem 8 A nearsighted person has a far point of 18 cm. What power contact lenses will allow this person to comfortably see distant objects clearly? A) +5.6 diopters B) -5.6 diopters C) diopters D) diopters Answer: B

22 Problem 9 The objective lens of a microscope has a focal length of 2.4 mm and the eyepiece has an angular magnification of 15. The object is positioned mm beyond the focal point of the objective. The focal point of the eyepiece is positioned at the real image formed by the objective. The near point of the microscope user is at 25 cm. What is the magnitude of the overall magnification of the microscope? Answer: 600