A camera lens usually consists of a combination of two or more lenses to produce

Question

A camera lens usually consists of a combination of two or more lenses to produce a good-quality image. Suppose a camera lens has two lenses - a diverging lens of focal length 10.5 cm and a converging lens of focal length 5.25 cm. The two lenses are held 7.77 cm apart. A flower of length 10.5 cm, to be pictured, is held upright at a distance 54.9 cm in front of the diverging lens; the converging lens is placed behind the diverging lens.
a) How far to the right of the convex lens is the final image?
b) What is the magnification of the final image?
c) And what is the height of the final image?

Explanation / Answer

Part A)

Start with the diverging lens

1/f = 1/p + 1/q

1/-10.5 = 1/54.9 + 1/q

q = -8.81 cm

The negative means its formed 8.81 cm in front of the diverging lens. Since the lenses are 7.77 cm apart, this distance is 16.58 cm from the converging lens

1/f = 1/p + 1/q

1/5.25 = 1/16.58 + 1/q

q = 7.68 cm

So the final image is formed 7.68 cm to the right of the converging lens

Part B)

The magnification of the first lens is M = -q/p = -(-8.81)/(54.9) = .16

For the second lens M = -q/p = -7.68/16.58 = -.463

Total magnification is (.16)(-.463) = -.074

Part C)

M = h'/h

(.074) = -h'/10.5

h' = -.778 cm   (The negative means its inverted)

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

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