Optometrists use an instrument called a keratometer to measure the curvature of

Question

Optometrists use an instrument called a keratometer to measure the curvature of the cornea. To apply this technique, an object of height 1.30 cm is held 3.00 cm from a patient's cornea, and its reflected image is measured. Because the cornea acts like a convex mirror, the resulting reflected image is upright and has a height of 0.185 cm. IS What is the magnification of the mirror formed by the cornea? What is the focal length of the mirror? Remember the sign convention for mirrors! Finally, what is the magnitude of the radius of curvature of the cornea? Magnification Mirror focal length Comea's radius of curvature Number Number Number cm cm

Explanation / Answer

Given,

h = 1.3 cm ; o = 3 cm ; h' = 0.185 cm

We know from the defination of magnification

M = -i/o = h'/h

M = 0.185/1.3 = 0.142

Hence, M = 0.142

from lens eqn, we know that

1/f = 1/i + 1/o

f = i x o/(i + o)

i = -M o = -0.142 x 3 = -0.427

f = -0.427 x 3/(-0.427 + 3) = -0.498 cm

Hence, f = -0.498 cm

R = 2f = 2 x 0.496 = 0.996 cm

Hence, R = 0.996 cm

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

---

---

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