A thin double convex lens is to focus the image of an object onto a screen so th

Question

A thin double convex lens is to focus the image of an object onto a screen so that the image is life-sized. The lens has equal radii of 55 cm and the refractive index is n = 1.5. (a) What is the distance d from image to screen? (b) What is the total distance L between object and image?
A thin double convex lens is to focus the image of an object onto a screen so that the image is life-sized. The lens has equal radii of 55 cm and the refractive index is n = 1.5. (a) What is the distance d from image to screen? (b) What is the total distance L between object and image?
(a) d = 110 cm
(b) L = 220 cm
(a) d = 220 cm
(b) L = 440 cm
(a) d = 55 cm
(b) L = 28 cm
(a) d = -110 cm
(b) L = -220 cm

Explanation / Answer

Part A)

First we need the focal length of the lens using the Lens Maker's Equation

1/f = (n - 1)(1/R1 - 1/R2)

1/f = (1.5 - 1)(1/55 - 1/-55)

f = 55 cm

Then since the image is "Life sized" the magnification is 1

Since M = -q/p

then q = -p

To have q and p is equal in magnitude, the object is placed at 2f, and thus the image is also found on the other side of the lens at 2f, therefore

q = 2f = 2(55) = 110 cm

Part B)

Since q and p are equal, and have a value of 110 cm, then q + p = 220 cm

Therefore, the correct solution is choice "a"

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.