Physics 2212
Midterm #3
April 14, 2014
Due April 16, 2014
Do not open exam until instructed
Questions 1-2 are worth 1 point each
Questions 3-8 are worth 3 points each
Not all questions are of equal difficulty
Attempt all questions – partial points may be awarded for work shown even if the final answer is
incorrect
Useful constants:
c = 3 x 108 m/s
e = 1.6 x 10-19 C
melectron = 9.11 x 10-31 kg
mproton = 1.67 x 10-27 kg
1) Imagine that the dispersion of light in water was such that the index of refraction was higher for
red light than blue light. How would this affect a rainbow?
2) According to Rayleigh’s Criterion, what are the only two ways in which the limit of the angular
resolution of a circular aperture can be improved?
3) A magnifying glass has a focal length of 8.0 cm. How close to an object do you need to place the
magnifying glass so that the distance between the image and the magnifying glass is the same as
the focal length? What type of image is this and what is its magnification?
4)
A refracting telescope has a eyepiece with a focal length of 0.6 cm and an objective lens with a
focal length of 32 cm. What is the magnification of this telescope? Draw the ray diagram for the
telescope.
5) Monochromatic light in a vacuum is incident on a screen with a diffraction grating, and a
diffraction pattern is created on a parallel screen placed 22 cm behind the first screen. In the
diffraction pattern the distance between two adjacent maxima is 0.65 mm. The distance
between the two adjacent slits in the grating is 250 μm. What is the frequency of the light?
6) A spy satellite is orbiting the earth at an altitude of 250 km. It has a round camera lens with a
radius of 35 cm which takes pictures using light with a wavelength of 550 nm. What is the
smallest distance the camera can resolve on the surface of the earth?
7) A soap film is formed in air. What is the thinnest the film can be in order for red light with a
wave length of 670 nm to interfere destructively upon reflection?
8) In a double slit diffraction experiment light of wavelength 480 nm is shone through a screen in
which two slits have been cut which are 1300 nm apart. A second parallel screen is placed 45 cm
behind the first screen. What is the distance between the 1st and 2nd interference minima on the
second screen? What is the distance between the 2nd and 3rd interference minima on the second
screen?