Question 1-4 refer to magnifying lenses. The human eye converges light forming a
ID: 2017014 • Letter: Q
Question
Question 1-4 refer to magnifying lenses. The human eye converges light forming an image on the retina, located about 2.5 cm behind the lens. the shape of the lens can be changed to focus on objects at distances from infinitely far off to about 25 cm. magnifying lenses take objects closer than 25 cm and produce their enlarged images farther away than 25 cm. angular magnification, which is NOT the same as lateral magnification (-i/o), is the angle subtended by the image divided by the angle subtended by the object if it were at 25 cm from the eye. for small angles when the object is just inside the focal point, the angular magnification of a simple magnifying lens can be approxiated as: m=0.25P where P is the power of the lens and .25 represents the minimum distance in meters that an object can still be brought into focus
1)What is the angular magnification of a convex lens with a focal length of 5 cm?
a. 1.25 b. 5 c. 10 d. 20
2) A simple magnifier has an angular magnification of 5. How large will the image of a 3 cm object be, if viewed through this lens?
a. 3 cm b. 6 cm c. 9 cm
d. more information is required to determine the size of the image
3)
The lens of the eye above is unable to focus the image of a distant object onto the retina. which lens could assist the eye to refocus the image onto the retina?
a. II only b. III only c. I and II only d. I and III only
4)
The lens of the eye above is unable to focus the image of a distant object onto the retina. which lens could assist the eye to refocus the image onto the retina?
a. II only b. III only c. I and II only d. I and III only
Explanation / Answer
(1) Focal length, f = 5 cm = 0.05 m Power of the lens, P = 1/f = 1/0.05 = 20 D Angular magnification, m = 0.25 P = 0.25 * 20 = 5 Ans: Option-b: m = 5 (2) Option - d: more information is required todetermine the size of the image (3) The person is suffering from nearsightedness (or) myopia. It can be corrected by using diverging lens. Ans: Option - b : III only (4) The person is suffering from farsightedness (or) hyperopia. It can be corrected by using converging lens. Ans: Option - c : I and II only The person is suffering from farsightedness (or) hyperopia. It can be corrected by using converging lens. Ans: Option - c : I and II only
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