A 5.93-mrrvhigh firefly sits on the axis of, and 12.5 cm In front of, the thin l

Question

A 5.93-mrrvhigh firefly sits on the axis of, and 12.5 cm In front of, the thin lens A, whose focal length is 5.11 cm. Behind lens A there is another thin lens, lens B, with focal length 21.5 cm. The two lenses share a common axis and are 58.5 cm apart. Is the image of the firefly that lens B forms real or virtual? How far from lens B is this image located (expressed as a positive number)? What is the height of this image (as a positive number)? Is this image upright or inverted with respect to the firefly?

Explanation / Answer

for lens A

object distance = s1 = 12.5 cm

focal length f1 = 5.11 cm

from lens equation

1/s1 + 1/s1' = 1/f1

1/12.5 + 1/s1' = 1/5.11

s1' = 8.64 cm

magnification m1 = -s1'/s1 = -8.64/12.5 = -0.6912

for lens B

s2 = d - s1' = 58.5-8.64 = 49.86 cm

1/s2 + 1/s2' = 1/f2

1/49.86 + 1/s2' = 1/21.5

s2' = 37.8 cm

magnification m2 = -s2'/s2 = -37.8/49.86 = -0.758

total magnification M = m1*m2

hi/ho = M1*M2

hi = 5.93*0.6912*0.758 = 3.11 mm <<------answer

upright

Real

s2' = 37.8 cm

hi = 31.1 mm

upright

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

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