Expert: Daniel Mazur - 12/4/2006

Question
Hey
i would like you to check my answers to these questions and correct those that are wrong. I would also like you to explain those that were wrong and those i could not answer, because i am doing homeschool and have to study by myself without a teacher to explain thing to me.
I am in high school, age 16

Thanks

1.   An object 5 millimeters high is located 15 millimeters in front of a plane mirror. How far from the mirror is the image located?                           
     A. 5.0 millimeters
                       
     B. 7.5 millimeters
                       
           C. 15 millimeters   (my answer)                            
     D. 30 millimeters
                       
                           
2.   Which of the following values represents an index of refraction of an actual material?                           
     A. 0
                       
     B. 1 / 4
                       
     C. 1 / 2
                       
           D. 5 / 4       (my answer)                             
                           

3.   Which one of the following types of electromagnetic radiation causes certain substances to fluoresce?                           
          A. Ultraviolet rays      (my answer)                           
     B. Infrared waves
                       
     C. X rays
                       
     D. Cosmic rays
                       
                           

                          
4.   If a 72-candela light source is located at a distance of 3 meters from a surface, the illuminance on the surface is                           
          A. 8 lux.    (my answer)                           
     B. 24 lux.
                       
     C. 216 lux.
                       
     D. 648 lux.
                       
                           

                          
5.   If you're driving towards the sun late in the afternoon, you can reduce the glare from the road by wearing sunglasses that permit only the passage of light that's                           
           A. polarized in a vertical plane.     (my answer)                           
     B. polarized in a horizontal plane.
                       
     C. dispersed in a vertical plane.
                       
     D. dispersed in a spherical plane.
                       
                           

                          
6.   The term angle of deviation is used in reference to                           
     A. a polarizer.
                       
           B. a prism.    (my answer)                           
     C. a lens.
                       
     D. an analyzer.
                       
                           

                          
7.   According to the information in your study unit, which of the following locations requires the highest illuminance?                           
     A. A residential stairway
                       
     B. A school locker room
                       
     C. A bank lobby
                       
           D. A study area    (my answer)                                 
                           
8.   The unit for measuring the rate at which light energy is radiated from a source is the                           
     A. Angstrom.
                       
     B. lux.
                       
           C. lumen.    (my answer)                           
     D. candela.
                       

                          
9.   Compared to yellow light, orange light has                           
     A. the same frequency.
                       
     B. a faster wave velocity.
                       
           C. a longer wavelength.  (my answer)                             
     D. a different polarization.
                       

                          
10.   The image formed by a convex spherical mirror will always be                           
     A. inverted and smaller than the object.
                       
           B. upright and smaller than the object.   (my answer)                           
     C. inverted and larger than the object.
                       
     D. upright and larger than the object.
                       

                          
11.   When an object is placed 8 millimeters from a concave spherical mirror, a clear image can be projected on a screen 16 millimeters in front of the mirror. If the object has a height of 4 millimeters, the height of the image is                           
     A. 2 millimeters.
                       
     B. 4 millimeters.
                       
          C. 8 millimeters.    (my answer)                           
     D. 12 millimeters.
                       

                          
12.   Which of the following lenses is a converging lens?                           
          A. Double-convex lens     (my answer)                           
     B. Spherical-convex lens
                       
     C. Plano-concave lens
                       
     D. Convexo-concave lens
                       

13.   A virtual image produced by a lens is always                           
     A. larger than the object.
                       
     B. smaller than the object.
                       
     C. located in front of the lens.    (my answer)
                       
     D. located in the back of the lens.  
                       
                          
14.   In which of the following materials is the velocity of light greatest?                           
        A. Air    (my answer)                           
     B. Water
                       
     C. Crown glass
                       
     D. Fused quartz
                       
                          
I don’t know this one   help
15.   If the distance from a converging lens to the object is less than the focal length of the lens, the image will be                           
     A. real, inverted, and larger than the object.
                       
     B. real, inverted, and smaller than the object.
                       
     C. virtual, upright, and larger than the object.
                       
     D. virtual, upright, and smaller than the object.
                       
                          
16.   When a simple magnifying glass is used properly, the image will be formed                           
     A. just inside the focal length of the lens.
                       
        B. about 250 millimeters in front of the lens.     (my answer)                           
     C. at the focal point of the lens.
                       
     D. about 500 millimeters behind the lens.
                       
                          
17.   When the image of a distant object is brought into focus in front of a person's retina, the defect is called                           
           A. nearsightedness.     (my answer)                           
     B. farsightedness.
                       
     C. chromatic aberration.
                       
     D. spherical aberration.
                       

                          
18.   Reflecting telescopes are popular because they're                           
     A. more powerful than a refracting telescope.
                       
     B. smaller than a refracting telescope.
                       
           C. easier to build than a refracting telescope.         (my answer)                           
     D. more durable than a refracting telescope.
                       
                           
19.   In any one material, all electromagnetic waves have the same                           
     A. amplitude.
                       
     B. frequency.
                       
     C. wavelength.
                       
           D. velocity.           (my answer)                           
                           

                          
20.   Which of the following occurs when light is reflected from a rough or unpolished surface?                           
          A. The original pattern of the light is distorted.     (my answer)                           
     B. The original pattern of the light is preserved.
                       
     C. The angle of reflection is less than the angle of incidence.
                       
     D. The angle of reflection is greater than the angle of incidence.
                       
                           

                          
21.   An object is located 51 millimeters from a diverging lens. The object has a height of 13 millimeters and the image height is 3.5 millimeters. How far in front of the lens is the image located?                           
     A. 1.12 millimeters
                       
           B. 13.7 millimeters       (my answer)                             
     C. 51 millimeters  
                       
     D. 189 millimeters
                       
                           
22.   A failure of the red-sensitive nerves in the eye to respond to light properly causes                           
     A. astigmatism.
                       
     B. farsightedness.
                       
     C. chromatic aberration.
                       
           D. color blindness.   (my answer)                           
                           

I have no cue for the next two question……please help and explain                             
23.   When a beam of light passes at an oblique angle into a material of lower optical density, the angle of incidence is                           
     A. less than the angle of reflection.
                       
     B. less than the angle of refraction.
                       
     C. greater than the angle of reflection.
                       
     D. greater than the angle of refraction.
                       
                           

                          
24.   Rays of light incident on a lens and parallel to the principal axis of the lens converge                           
     A. at the center of curvature of the lens.
                       
     B. at the focal point of the lens.
                       
     C. in front of the lens.
                       
     D. in back of the lens.
                       
                           

                          
25.   If an object 18 millimeters high is placed 12 millimeters from a diverging lens and the image is formed 4 millimeters in front of the lens, what is the height of the image?                           
          A. 6 millimeters    (my answer)                           
     B. 8 millimeters
                       
     C. 14 millimeters
                       
     D. 22 millimeters
                       




THANKS

Answer
Hi,
You effectively asked for explanation of 25 different things and I cannot do that, I will give it half an hour total. Sorry, we are all volunteering here and the time we can spend with a single request is limited (I have a limit 3 requests per day, because each takes 15-45 minutes to answer.

1. You're right, because in a plane mirror the object and image distances are equal.
2. You're right, because the index of refraction is defined as n = speed-of-light-in-vacuum/speed-of-light-in-material, which must be bigger than 1.
3. You're right, it's what Wikipedia says. It cannot be Infra Red, because its wavelength is longer than visible light (i.e. it does not satisfy the one necessary condition for fluorescence). Cosmic rays and x-rays cause phosphorescence, because their wavelength is MUCH shorter than visible light, so other relaxation processes that photon absorption and photon emission are involved.
4. You're right, illumination drops with distance-squared.
5. You're right, because the glare is polarized horizontally by the total reflection from the horizontal road. To cut that down, your glasses should be polarized perpendicularly.
6. You're right, there's no explanation, you just gotta memorize the terminology.
7. Only your answer makes sense, I don't get it about "my study unit", though...
8. You're right, lux is an illuminance unit, Angstroem in a length unit and candela is lumen per stradian. Lumen is the total radiative power.
9. You're right, the sequence from long to short wavelength is red-orange-yellow-green-blue-violet. Nothing to explain, you just gotta remember.
10. You're right. This can hardly be explained without a picture, but one look at the back of your spoon gives you the experimental proof.

This is as far as I can go. Sorry, my time is up!