AP Physics 2 Questions: Lenses and Image Formation

📚 Quick Study Guide

• 🔍 Refraction: The bending of light as it passes from one medium to another.
• 💡 Snell's Law: Relates the angles of incidence and refraction to the indices of refraction of the media: $n_1\sin(\theta_1) = n_2\sin(\theta_2)$.
• 👓 Lenses: Transparent objects that refract light to form an image.
• 🔎 Converging Lenses: Thicker in the middle; converge parallel rays to a focal point. Have positive focal length ($f > 0$).
• 🔆 Diverging Lenses: Thinner in the middle; diverge parallel rays. Have negative focal length ($f < 0$).
• 📸 Thin Lens Equation: $\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}$, where $f$ is the focal length, $d_o$ is the object distance, and $d_i$ is the image distance.
• 📈 Magnification: $M = \frac{h_i}{h_o} = -\frac{d_i}{d_o}$, where $h_i$ is the image height and $h_o$ is the object height.
• 📏 Sign Conventions:
  • Object distance ($d_o$) is positive if the object is on the same side as the incoming light.
  • Image distance ($d_i$) is positive if the image is on the opposite side from the outgoing light (real image).
  • Focal length ($f$) is positive for converging lenses and negative for diverging lenses.
• 🎨 Real Images: Formed by actual convergence of light rays; can be projected onto a screen ($d_i > 0$).
• 👻 Virtual Images: Formed where light rays appear to diverge from; cannot be projected onto a screen ($d_i < 0$).

🧪 Practice Quiz

1. A converging lens has a focal length of 10 cm. An object is placed 30 cm from the lens. What is the image distance?
   1. 5 cm
   2. 15 cm
   3. 20 cm
   4. 30 cm
2. An object is placed 15 cm from a diverging lens with a focal length of -10 cm. What is the image distance?
   1. -6 cm
   2. 6 cm
   3. 30 cm
   4. -30 cm
3. What type of image is formed by a diverging lens when the object is placed at any distance from the lens?
   1. Real and inverted
   2. Real and upright
   3. Virtual and inverted
   4. Virtual and upright
4. If the magnification of an image is -2, what does this indicate about the image?
   1. The image is real, inverted, and twice the size of the object.
   2. The image is virtual, upright, and twice the size of the object.
   3. The image is real, upright, and half the size of the object.
   4. The image is virtual, inverted, and half the size of the object.
5. A lens forms a real image that is inverted and smaller than the object. What type of lens is it?
   1. Converging lens
   2. Diverging lens
   3. Planar lens
   4. Biconcave lens
6. If an object is placed at the focal point of a converging lens, where is the image formed?
   1. At the focal point
   2. At twice the focal length
   3. At infinity
   4. At the lens itself
7. What is the SI unit of focal length?
   1. Diopter
   2. Meter
   3. Centimeter
   4. No unit