SAMPLE EXAM FOR CH's 22, 23, 24

1] For each part below, an object 25.0 cm tall is located 40.0 cm in front of the mirror.

A) For an image formed at q = +120 cm, calculate the height of the image and state

whether it is real or virtual and whether it is erect or inverted.

Answer: -75 cm, real, inverted

B) For an image formed at q = - 5.0 cm,
calculate the radius of curvature of the mirror

and state whether it is concave or convex.

Answer: -11.4 cm , convex

2] Two thin lenses, each with a focal length, f = +20 cm, are placed 50 cm apart. An  object
             15 cm tall is placed 60 cm in front of the first lens. Where is the final image formed for the system?

Answer: No image is formed, q would be at infinity.

5]         A screen is separated from a double-slit source by a distance of 1.20 m.  The distance between
the slits is 0.030mm.  If light of wavelength 633 nm is incident on the slits, at what angle would you
find the 30th order bright fringe?

Answer: 39.3 degrees

6]  A submarine is 300 m horizontally out from the shore.  It is 100 m below
the surface.  A laser beam sent out from the sub strikes the surface of the water
at a point 210 m from the shore.  The beam exiting the water strikes the top of a
tower standing right at the water's edge on the shore.  Determine the height of
the tower.

Answer:  107 m

MULTIPLE CHOICE

1)  When total internal reflection happens at a glass to air interface
       a)  half the light is refracted
       b)  half the light is reflected
       c)  light hits the interface from the air side
       d)  light hits the interface from the glass side
       e)  the law of reflection ceases to hold

2)  When you see your image in a plane mirror, your image appears to be
       a)  in front of the mirror
       b)  at the surface of the mirror
       c)  behind the surface of the mirror at a distance equal to your distance from the mirror
       d)  behind the surface of the mirror at a distance equal to half your distance from the mirror

       e)  in front of the surface of the mirror at a distance equal to half your distance from the mirror

3)  In a camera using a simple lens, the image focused on the film would be
       a)  real and upright
       b)  real and inverted
       c)  virtual and upright
       d)  virtual and inverted
       e)  formed at infinity

4)  A general condition such that two waves will undergo destructive interference is
       a)  their phase difference is zero
       b)  their phase difference is +90 deg
       c)  their phase difference is + or - 90 deg
       d)  their phase difference is an even integral multiple of  lambda/2 (wavelengths)
       e)  their phase difference is an odd integral multiple of  lambda/2 (wavelengths)

5)   Increasing the wavelength in a double slit experiment has what effect on the position of maxima on a screen
      at a fixed distance?
       a)  maxima get closer together
       b)  maxima get farther apart
       c)  maxima get cancelled by minima
       d)  it has no effect

ANSWERS:

1.  d
2.  c
3.  b
4.  e

5.  b