# Concave Lens and Principal Focus Quiz

ProdigiousSlideWhistle
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## 9 Questions

### What is the nature of the image formed by a convex lens when the object is placed 15 cm from the lens?

Real and inverted

### If a concave lens is used instead of a convex lens with the same object distance of 15 cm, what would be the nature of the image?

Real and inverted

-2

### Based on the given information, where is the image formed by the convex lens located with respect to the optical center?

30 cm after the optical center

### What does a positive image distance indicate in the context of this problem?

Real image formed

### If a concave lens of short focal length were used instead, what would be the position of the image compared to a convex lens?

Farther from the optical center

Focal length

Power

### What happens to light rays when passing through a concave lens with very short focal length?

They diverge strongly

## Study Notes

### Action of a Concave Lens

• A concave lens refracts parallel rays of light, making them appear to diverge from a point on the principal axis, called the principal focus (F).
• A concave lens has two principal foci, F1 and F2, on either side of the lens.
• The distance between the principal focus and the optical center of a lens is its focal length (f).

### Image Formation by Lenses

• Lenses form images by refracting light.
• Image formation by a convex lens can be demonstrated using five parallel straight lines, a convex lens, and a lens stand.
• The mirror formula, 1/u + 1/v = 1/f, relates the object distance (u), image distance (v), and focal length (f).

### Magnification

• Magnification is the relative extent to which the image of an object is magnified with respect to the object size.
• Magnification (m) is expressed as the ratio of the height of the image (h') to the height of the object (h), m = h'/h.
• Magnification can also be expressed as m = -v/u, where v is the image distance and u is the object distance.

### Image Characteristics

• The height of the object is taken to be positive when placed above the principal axis.
• The height of the image is positive for virtual images and negative for real images.
• The nature, position, and size of an image can be determined by the object distance, image distance, and focal length.

### Power of a Lens

• The power of a lens is a measure of its ability to converge or diverge light rays.
• The power of a lens depends on its focal length, with shorter focal lengths resulting in larger convergence or divergence angles.

Test your knowledge on the action of a concave lens, including the concept of principal focus. Learn how parallel rays of light behave when passing through a concave lens and understand the significance of the principal focus point.

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