The nice thing about lenses is that the thin lens equation is the same as the mi

Question

The nice thing about lenses is that the thin lens equation is the same as the mirror equation. The magnification formula is also the same. In fact, depending on how you look at it, many of the signs are similar. Check out the Summary of Sign Conventions for Lenses in the text.
A 3.70-cm tall pencil is placed 11.0 cm in front of a lens. An image is formed 4.90 cm on the opposite side of the lens from the object. What is the focal length of the lens?

Is the lens converging or diverging?

Correct: Converging
Incorrect: Diverging

A 4.30-cm tall pencil is placed 13.9 cm in front of a lens. An image is formed 4.20 cm on the same side of the lens as the object. What is the focal length of the lens?

Is the lens converging or diverging?

Correct: Diverging
Incorrect: Converging

A 3.40-cm tall pencil is placed 11.0 cm in front of a lens. The focal length of the lens is +27.5 cm. What is the image distance (with proper sign)?

Is the image real or virtual?

Incorrect: Real
Correct: Virtual

Explanation / Answer

Part 1)

Apply 1/f = 1/p + 1/q

1/f = 1/11 + 1/4.9

f = 3.39 cm

Part 2)

The lens is converging

Part 3)

1/f = 1/p + 1/q

1/f = 1/13.9 + 1/-4.2

f = -6.02 cm

Part 4)

The lens is diverging

Part 5)

1/f = 1/p + 1/q

1/27.5 = 1/11 + 1/q

q = -18.3 cm

Part 6)

The image is virtual

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

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