Images Formed by Lenses - AP Physics 2

1. What happens to the image if the object is moved closer to a lens than the focal point?

   Image becomes virtual and upright. Object inside focal length produces virtual, upright image.

2. If $f = 20$ cm and $d_o = 30$ cm, calculate $d_i$ for a convex lens.

   $d_i = 60$ cm. Using lens formula: $\frac{1}{20} = \frac{1}{30} + \frac{1}{d_i}$

3. Find the image distance if $f = 10$ cm and $d_o = 15$ cm for a convex lens.

   $d_i = 30$ cm. Using lens formula: $\frac{1}{10} = \frac{1}{15} + \frac{1}{d_i}$

4. What does a negative magnification value indicate?

   Image is inverted. Negative magnification means image is flipped vertically.

5. Find the focal length if power of lens is $+5$ D.

   $f = 0.2$ m. Power equals reciprocal of focal length: $f = \frac{1}{5}$

6. Calculate magnification if $d_o = 10$ cm and $d_i = -5$ cm.

   $m = 0.5$. Magnification equals negative ratio: $m = -\frac{(-5)}{10} = 0.5$

7. Calculate focal length if the power of the lens is $-4$ D.

   $f = -0.25$ m. Focal length equals reciprocal of power: $f = \frac{1}{-4}$

8. How does image distance relate to object distance for a real image in a lens?

   Image distance $d_i$ is positive. Real images form on opposite side of lens from object.

9. What is the outcome if an object is placed at the center of curvature of a convex lens?

   Image is real, inverted, and same size. Object at center of curvature equals twice focal length.

10. Find the image height if $h_o = 2$ cm and $m = 3$.

    $h_i = 6$ cm. Image height equals object height times magnification.

11. Identify the type of lens used in a magnifying glass.

    Convex lens. Converging lens creates enlarged virtual image for close objects.

12. When is an image formed by a lens virtual?

    When image distance $d_i$ is negative. Negative $d_i$ means image forms on same side as object.

13. What type of image is formed by a lens if the object is placed between the lens and the focal point?

    Virtual and magnified. Object inside focal length produces enlarged virtual image.

14. What is the lens formula?

    $\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}$. Relates focal length to object and image distances.

15. Determine the power of a lens with focal length $-0.5$ m.

    $P = -2$ D. Negative power indicates diverging lens: $P = \frac{1}{-0.5}$

16. Which lens type converges light rays?

    Convex lens. Brings parallel rays together at focal point.

17. Find the image distance if $f = 12$ cm and $d_o = 24$ cm for a convex lens.

    $d_i = 24$ cm. Using lens formula: $\frac{1}{12} = \frac{1}{24} + \frac{1}{d_i}$

18. What is the effect of increasing object distance on image size in a convex lens?

    Image size decreases. Magnification decreases as object distance increases.

19. What is the relationship between curvature and power of a lens?

    More curvature, higher power. More curved surfaces bend light more, increasing power.

20. Identify the image when an object is placed at infinity for a convex lens.

    Real, inverted, and at F. Parallel rays from infinity converge at focal point.

21. Identify the type of image formed by a convex lens when object is beyond 2F.

    Real, inverted, and reduced. Object farther than twice the focal length produces these characteristics.

22. What is the unit of power for lenses?

    Diopter (D). Standard unit for measuring lens refractive power.

23. Which type of lens corrects hyperopia?

    Convex lens. Converging lens focuses light to correct farsightedness.

24. What is the nature of the image formed when an object is placed at 2F of a concave lens?

    Virtual, upright, and reduced. Concave lenses always produce diminished virtual images.

25. Which type of lens corrects myopia?

    Concave lens. Diverging lens spreads light to correct nearsightedness.

26. State the sign convention for focal length of a concave lens.

    Focal length is negative. Concave lenses diverge light, making $f$ negative by convention.

27. What is the power of a lens formula?

    Power $P = \frac{1}{f}$ (in meters). Reciprocal of focal length measured in meters.

28. What is the magnification formula for lenses?

    Magnification $m = \frac{h_i}{h_o} = -\frac{d_i}{d_o}$. Ratio of image to object height equals negative distance ratio.

29. Which lens type always forms a virtual image?

    Concave lens. Diverging lens cannot form real images regardless of object position.

30. Explain the sign of $d_i$ for virtual images.

    $d_i$ is negative. Virtual images form on same side as object.

31. Describe the image when an object is at the focal point of a convex lens.

    No image is formed. Parallel rays emerge, creating no convergence point.

32. Determine the magnification for $d_o = 25$ cm and $d_i = 50$ cm.

    $m = -2$. Magnification equals negative distance ratio: $m = -\frac{50}{25}$

33. State the effect of lens curvature on focal length.

    More curvature, shorter focal length. Greater curvature increases light bending, reducing focal length.

34. Identify the image characteristics when object is between F and 2F of a convex lens.

    Real, inverted, and magnified. Object between focal points creates enlarged real image.

35. State the relation between object distance, image distance, and magnification.

    $m = -\frac{d_i}{d_o}$. Negative sign accounts for image orientation relative to object.

36. Define focal length for a lens.

    Distance from lens center to focal point. Where parallel rays converge or appear to diverge.

37. Identify the nature of the image formed by a concave lens.

    Virtual, upright, and reduced. Concave lenses always diverge light, creating virtual images.

38. What type of image is formed at 2F by a convex lens?

    Real, inverted, and same size. Object at twice focal length creates unit magnification.

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