Physics 202 MWF 10:20 Spring 1998 (Ford)
Exam IV Chapts. 36-39 in SZY College Physics 7e


Show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.


(16 pts) 1.
a) A farsighted eye has a near point of 150 cm. What is the focal length of the lens, placed very close to the eye, that will correct the vision so that the eye can clearly view objects that are a distance of 25 cm from the eye? Is the lens converging (positive f) or diverging (negative f)?

Ans. f = ___+30 cm____

converging or diverging? ___converging___

b) A nearsighted eye has a far point of 400 cm. What is the focal length of the lens, placed very close to the eye, that will correct the vision so that the eye can clearly view objects that are a large distance from the eye? Is the lens converging (positive f) or diverging (negative f)?

Ans. f = ___-400 cm____

converging or diverging? ___diverging___


(12 pts) 2. A ray of light traveling in glass is incident on the surface of the glass at an angle ø_a with respect to the normal. It is observed that there is no light refracted into the air when ø_a is greater than 37°.

a) What is the refractive index of the glass?

Ans. ___1.66___

b) If the wavelength of the light in the glass is 400 nm, what is its wavelength in air?

Ans. ___665 nm___


(12 pts) 3. Unpolarized light with intensity I₀ is incident on a polarizing filter, and the emerging light strikes a second filter with its axis at 30° to that of the first. In terms of I₀, what is the intensity of the light after it has passed through the second polarizer?

Ans. __0.375I₀ _____________


(16 pts) 4. An object 4.0 mm tall is 20 cm to the left of a spherical mirror. The image is 3.0 mm tall and is erect. What is the radius of curvature of the mirror? Is the mirror concave or convex?

Ans. R = __-120 cm___

concave or convex? __convex___

(20 pts) 5. Light from a very distant object is incident on a glass sphere that has index of refraction 1.5 and radius |R|=15 cm. How far is the final image from the center of the sphere? Is the final image real or virtual?

Ans. distance from center of sphere ___22.5 cm___

real or virtual ___real___


(24 pts) 6. An object 2.0 mm tall is placed 40 cm to the left of a converging lens that has focal length f₁ = +20 cm. A second converging lens, with focal length f₂ = +10 cm is 5 cm to the right of the first lens.

a) How far is the final image from the object?

Ans. ___52.8 cm to right____

b) Is the final image real or virtual?

Ans. ___real___

c) Is the final image erect or inverted?

Ans. ___inverted____

d) What is the height of the final image?

Ans. ___0.446 mm___