Practice Problems - Test 3

1. A distance to be measured by reflecting a pulse of laser light from a mirror andmeasuring the total time taken for the pulse to return to a detector at the site of the laser. How much time elapses for a distance of 152 m?

2. A certain laser produces a cylindrical beam of light with a diameter of 1.5mm and an average power of 1.5 W.  The laser beam can be focused by a lens to a circular spot 2.0 micrometer in radius. 
(a) What is the average intensity of the focused beam? (b) What are the maximum values of the electric and magnetic fields in the focused beam?

3. Linearly polarized light falls on a sheet of polarizing material whose transmission axis is oriented at an angle, ø, to the direction of polarization of the light.  What fraction of the incident intensity is transmitted through the sheet for
ø = 15.0, 30.0, 60.0, and 75.0 degrees?

4. The lowest frequency of visible light corresponds to the color _____.
(a) blue   (b) green   (c) red   (d) yellow

5. Which of the following cannot travel through a vacuum?
(a)microwaves   (b) visible light   (c) x-rays   (d)  sound

6. The electric field in an electromagnetic wave has an rms. strength of 150 N/C.  What is the rms. strength of the magnetic field in the wave? (a) 5x10^-7 T   (b) 4.5x10¹⁰ T   (c) 7.07x10^-7 T   (d) 6.63x10¹⁰ T

7. A 179 cm tall boy wants to buy a mirror that is tall enough so he can see himself full length in the mirror.  What is the minimum height of such a mirror?

8. A concave spherical mirror has a radius of curvature of 100 cm.  What is its focallength?
(a) 50 cm   (b) 100 cm   (c) 200 cm   (d) 300 cm

9. Light reflected from a fish strikes the surface of the water at an angle of 38 degrees to the normal.  What is the angle of refraction of the light into the air?

10. A clear spring has white shells on its bottom which appear to the occupants of a glass bottom boat to be only 45.0 ft below.  What is the actual depth of the spring?

11. The light reflected from a solid of unknown refractive index is 100% horizontallypolarized when the light strikes the solid at an angle of 65 degrees to the normal.  What is the index of refraction of the solid?

12. If a real object is placed inside the focal point of a concave mirror, the image is
(a) real and upright   (c) virtual and upright   (b) real and inverted   (d) virtual and inverted

13. The image formed by a convex spherical mirror is
(a)sometimes real, sometimes virtual (b) sometimes erect, sometimes inverted  (c) always real and inverted (d)always virtual and upright

14. Convex spherical mirrors produce images which are
(a) always larger than the actual object
(b) always smaller than the actual object (c) always the same size as the actual object
(d) sometimes larger, sometimes smaller

15. A man is 6.0 ft tall.  What is the smallest plane mirror he can use to see his entire image?
(a) 3.0 ft   (b) 6.0 ft   (c) 12 ft   (d) 24 ft

16. An object is placed at the radius of curvature of a concave spherical mirror.  The image formed by the mirror is
(a)located at the focal point of the mirror. (b) located between the focal point and the radius of curvature of the mirror. (c) located at the center of curvature of the mirror. (d) located out beyond the center of curvature of the mirror.

17. An object is placed 60 cm in front of a concave mirror.  The real image formed by the mirror is located 30 cm in front of the mirror.  What is the object's magnification? (a) +2   (b) -2   (c) +0.5   (d) -0.5

18. An object is placed 60 cm in front of a convex mirror.  The virtual image formed by the mirror is located 30 cm behind the mirror.  What is the object's magnification? (a) +2   (b) -2   (c) +0.5   (d) -0.5

19. An object is placed 20.0 cm in front of a concave mirror whose focal length is 25.0 cm.  Where is the image located? (a) 100 cm in front of the mirror  (c) 50 cm in front of the mirror (b) 100 cm behind the mirror  (d) 50 cm behind the mirror

20. An object is placed 20.0 cm in front of a concave mirror whose focal length is 25.0 cm. What is the magnification of the object? (a) +5.0   (b) -5.0   (c) +0.20   (d) -0.20

21. An object is placed 40.0 cm in front of a convex mirror.  The image appears 15 cm behind the mirror.  What is the focal length of the mirror?  (a) +24 cm   (b) +11 cm   (c) -11 cm   (d) -24 cm

22. An object is placed in front of a concave mirror of local length 50.0 cm and a real image is formed 75 cm in front of the mirror.  How far is the object from the mirror? (a) 25 cm   (b) 30 cm   (c) 150 cm   (d) -150 cm

23. Complete the following table.  As an example, the first row of the tableshows a completed set of data.

 
bhatti@panam.edu