Physics 197

Chapter 31,32,33

Practice exam

Sample Conceptual Problems: Do all 5 Problems. (2 points apiece)

 

  1. Rank the following concave mirror images from smallest to largest, according to object position relative to focal length

a). Object distance = 5 x f

b). Object distance = 2 x f

c). Object distance = 6 x f

c,a,b

  1. In which of the following mirror images will we produce a real image

a). Convex mirror, object positioned anywhere

b). Concave mirror, object outside of center of curvature

c). Concave mirror, object anywhere inside center of curvature

d). Concave mirror, object outside focal length

b,d

3. A mirror produces a virtual image that is ½ times the size of the object. What type of mirror is it?

a). Concave

b). Convex

b

4.  The net phase change due to a pair of reflections off a thin film and its substrate is p. What is the resultant interefrence when the thickness of the film is 10 wavelengths of the incident monochromatic light?

(a). destructive

(b). constructive

(c). both a and b

(d). neither a or b

d

5. When a light ray moves from a higher to a lower refractive index the ray

(a) bends towards the normal

(b). bends away from the normal

(c). travels in a non-deviated straight line

b

Sample Low Difficulty problems: Do all 4 Problems (10 points apiece):

All work must be shown for full credit!

 

1. An object is placed 35cm from a concave mirror of focal length 22 cm. Determine the image position, and magnification.

2. A real image from a converging lens appears 45 cm from a convex lens of focal length 12 cm.

Determine the object position.

3. Determine the vertical displacement of the 4th bright fringe from the central fringe in a Young's double slit experiment, when the slit separation is .125 mm, the distance from the slits to the screen is 1.25 m, and the incident wavelength is 556 nm.

4. Determine the speed of light when it travels from air to a material of refractive index 3.7.

 

Sample Advanced Difficulty Problems: Do any 4 of the following problems. (25 points apiece).

All work must be shown for full credit!

 

1.    Derive the following expression completely:

 Two lenses are in combination. Show that the total magnification of the system is the product of the individual magnifications.

 

See chapter 32 extra credit

2. In considering reflection and transmission between two boundary mediums, at near normal incident angles, the intensity of a reflected light ray IR is given by:

IR = Io [(n1-n2)/ (n1+n2)] 2

Where Io is the incident intensity, n1 and n2 are the refractive indexes of the two boundary mediums, and Io = IR + IT, where IT is the transmitted intensity.

Consider a plate of glass in air. Show that the transmitted intensity through both surfaces of the plate is given by the expression:

    IT = Io [4n/ (n2 + 1)2]2

See chapter 31 extra credit problem

 

3. Two convex lenses are separated by the sum of their focal lengths. The first lens has a focal length of 150cm, while the second has a focal length of 120 cm. If a 10 cm high object is placed 440 cm from the first lens, determine the final image position relative to the 150 cm lens, the final image height and orientation.

 

4. A thin film of refractive index 1.23 lies on a substrate of refractive index 1.65. When the film is illuminated with white light, the only two wavelengths visible are 456 nm and 576 nm. Determine the thickness of the thin film.

 

       

 

 

5. A circular blue light source is placed at the bottom of a 15 foot deep swimming pool, filled with a liquid of refractive index 2.3. Determine the area of the blue circular light seen on the surface.

 

 

6. An object is placed 25 cm from a concave refracting surface. The surface has a radius of curvature of 5 cm, and the refractive index is 1.70. Determine the refracted image position and orientation.

 

 

7. A polarizer is followed by n analyzers, each tilted by .540 with respect to the pervious. How many analyzers are required to reduce the intensity by a factor of 1/50 that which is entering the polarizer?