Question

1. A Michelson interferometer uses light with a wavelength of 562.446 nm. Mirror M2 is slowly moved a distance x, causing exactly 4.7200×102 bright-dark-bright fringe shifts to be observed starting and ending with a central bright spot. If the mirror moved only half the distance, what would the final image be?

a. Bright spot

b. Dark spot

c. In between bright and dark spots

d. Impossible to determine, more information needed

2. Starting at the surface of a convex mirror and walking away from it, your image in the mirror

a. changes from being a virtual image to a real image as you pass the focal point.

b. is always a real image, no matter how far you are from the mirror.

c. decreases in height.

d. is always the same height.

e. may or may not decrease in height, depending on your distance from the mirror.

3. A convex lens has a focal length f. An object is between 2f and 1f on a line perpendicular to the center of and in front of the lens. The image formed is located at what distance behind the lens?

a. 2f

b. between the lens and f

c. between f and 2f

d. farther than 2f

e. f

4. A camera takes a properly exposed photo with a 4.0 mm diameter aperture and a shutter speed of 1/250 s. If the photographer focuses on the same point, but the diameter to 2.00 mm, what needs to happen to the shutter speed, if it is still properly exposed?

a. Nothing

b. Increases by 4

c. Decreases by 1/4

d. Increases by 2

e. Decreases by 1/2

5. A person has many convex lenses with only two different focal lengths (short and long) which configuration makes the best telescope (built correctly)?

a. a short focal length objective and a short focal length eyepiece.

b. a long focal length objective and a short focal length eyepiece.

c. a long focal length objective and a long focal length eyepiece.

d. a short focal length objective and a long focal length eyepiece.

Answer 1

2. Answer (c) : Convex mirrors always form virtual images, and they reduce in size as the object moves farther.

3. Answer (d) : A convex lens forms a real and enlarged image when the object is between f and 2f, and this image is located farther than the 2f point. (see diagram below)

4. Answer (c) : Reducing the aperture diameter from 4mm to 2mm, reduces the light exposure by 1/4th (because area is proportional to the square of the diameter). So in order to balance this reduced light exposure, the shutter needs to stay open for 4 times longer duration, i.e. shutter speed decreased by 1/4th

5. Answer (b) : In an Astronomical telescope (both convex lenses), the objective lens must have a longer focal length because the magnification is equal to the objective focal length divided by the eye-piece focal length. Thus, for a better magnification, the objective lens must have a longer focal length than the eye-piece.