Optics: Lenses and Their Properties
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Questions and Answers

What is the relationship between object distance and image size when the object is positioned further than twice the focal length from a convex lens?

  • The image does not form.
  • The image is the same size as the object.
  • The image is smaller than the object. (correct)
  • The image is larger than the object.

What acronym can be used to remember the properties of images in ray diagrams?

  • SALT (correct)
  • SHAPE
  • SLEET
  • SAIL

If an object is placed between the focal point and the optical center of a convex lens, what type of image is formed?

  • Virtual Image (correct)
  • Real Image
  • Inverted Image
  • Diminished Image

When describing the image formed by a convex lens, which of the following properties indicates that the image is upside down?

<p>Attitude (C)</p> Signup and view all the answers

What happens to an image when the object is placed at a distance between the focal point and twice the focal length of a convex lens?

<p>The image becomes larger than the object. (D)</p> Signup and view all the answers

In ray diagrams, which component represents the point where light rays converge or appear to diverge from?

<p>Focal Point (B)</p> Signup and view all the answers

What is the principal focus of a converging lens?

<p>The point where incident rays converge after refraction (D)</p> Signup and view all the answers

What is indicated by a positive value for the image distance in lens formulas?

<p>The image is real. (C)</p> Signup and view all the answers

Which term describes the distance from the principal focus to the optical center of the lens?

<p>Focal length (D)</p> Signup and view all the answers

When using a convex lens as a magnifying glass, the object is placed at which position?

<p>Within the focal length. (D)</p> Signup and view all the answers

What is the significance of the point labeled as 2F on a convex lens?

<p>It is called the center of curvature of the lens (D)</p> Signup and view all the answers

Which of the following best defines a virtual image?

<p>An image that cannot be projected onto a screen (D)</p> Signup and view all the answers

How does a diverging lens differ in its principal focus compared to a converging lens?

<p>Rays appear to diverge from the focus (C)</p> Signup and view all the answers

Which statement about the magnification produced by lenses is accurate?

<p>Magnification is defined as the ratio of image size to object size (D)</p> Signup and view all the answers

What is the relationship between focal length and magnification in lenses?

<p>Longer focal lengths produce a narrower angle of view and higher magnification. (A)</p> Signup and view all the answers

Which of the following statements about real and virtual images is true?

<p>Real images can be formed on a screen. (A), Virtual images cannot form on a screen and are typically erected. (B)</p> Signup and view all the answers

What determines the angle of view for a lens?

<p>The focal length of the lens (D)</p> Signup and view all the answers

What happens to light rays when they pass through the optical center of a lens?

<p>They travel in a straight line without deviation (D)</p> Signup and view all the answers

What does a magnification value less than 1 indicate about an image?

<p>The image is smaller than the object. (C)</p> Signup and view all the answers

Which statement is correct regarding ray diagrams?

<p>Three principal rays are used to estimate the location of an image. (A)</p> Signup and view all the answers

In the equation for magnification, which variables are used to express it?

<p>Object distance and image distance. (A), Height of the image and height of the object. (C)</p> Signup and view all the answers

What characteristic differentiates a flashlight from a telescope?

<p>Flashlights send out parallel beams of light which do not converge. (C)</p> Signup and view all the answers

What happens to the angle of view when using a shorter focal length lens?

<p>The angle of view widens but magnification decreases. (D)</p> Signup and view all the answers

For a focused image to be formed, where must the camera film be placed relative to the lens?

<p>At a distance corresponding to the calculated magnification. (B)</p> Signup and view all the answers

What happens to the size of an image when an object is placed at a distance greater than twice the focal length from a convex lens?

<p>The image becomes smaller than the object (C)</p> Signup and view all the answers

Which property describes the location of an image formed by a convex lens when the object is placed between F and 2F?

<p>The location is beyond 2F (B)</p> Signup and view all the answers

What type of image is formed when the object is positioned less than the focal length from a convex lens?

<p>Virtual image (D)</p> Signup and view all the answers

What does the acronym SALT stand for when analyzing image properties in ray diagrams?

<p>Size, Attitude, Location, Type (B)</p> Signup and view all the answers

If an object is positioned at infinity relative to a convex lens, what characteristic does the image have?

<p>The image is real and smaller (D)</p> Signup and view all the answers

When using a convex lens for projection, what occurs to the size of the image compared to the object when the object is placed between 2F and F?

<p>The image appears larger (D)</p> Signup and view all the answers

Which of the following statements is true regarding the behavior of light rays passing through a convex lens?

<p>Rays parallel to the principal axis converge at F (B)</p> Signup and view all the answers

What indicates that a negative image distance signifies in lens formulas?

<p>The image is virtual (C)</p> Signup and view all the answers

What effect does a longer focal length have on magnification and angle of view?

<p>Decreases angle of view, increases magnification (B)</p> Signup and view all the answers

Where are real images formed in relation to a lens?

<p>On the opposite side of the lens (B)</p> Signup and view all the answers

What does it indicate if a magnification value is less than 1?

<p>The image is smaller than the object (D)</p> Signup and view all the answers

What does a virtual image indicate about the paths of light rays?

<p>Light rays diverge after changing direction (D)</p> Signup and view all the answers

In a ray diagram, how does a ray behave when it travels parallel to the principal axis before reaching the lens?

<p>It passes through the focal point (C)</p> Signup and view all the answers

What is the relationship between object distance and image size when the object is positioned less than the focal length from a converging lens?

<p>The image is virtual and larger (D)</p> Signup and view all the answers

Which principle describes the behavior of rays when constructing ray diagrams for lenses?

<p>Only the central ray passes straight through the center of the lens (C)</p> Signup and view all the answers

How does the angle of view change when using a shorter focal length lens?

<p>It becomes wider and increases in magnification (D)</p> Signup and view all the answers

What is the principal axis of a lens defined as?

<p>The line that intersects the lens at its optical center. (C)</p> Signup and view all the answers

Which characteristic is true for a real image formed by a converging lens?

<p>It is inverted and can be projected on a screen. (B)</p> Signup and view all the answers

What does the focal length of a lens indicate?

<p>The distance from the optical center to the principal focus. (B)</p> Signup and view all the answers

When light rays are noted as coming from an object at infinity, what can be assumed about these rays?

<p>They travel parallel to each other. (B)</p> Signup and view all the answers

What is the significance of the 2F point in a lens system?

<p>It is the center of curvature of the lens. (A)</p> Signup and view all the answers

Which statement accurately describes a diverging lens?

<p>It has a negative focal length. (B)</p> Signup and view all the answers

How does the optical center of a lens affect light rays passing through it?

<p>It allows light rays to travel through without deviation. (A)</p> Signup and view all the answers

What happens to the angle of view when a longer focal length lens is used?

<p>The angle of view decreases, capturing less of the scene. (D)</p> Signup and view all the answers

Flashcards

Converging Lens

A lens that causes parallel light rays to converge (meet at a point).

Principal Axis

An imaginary line passing through the center of a lens.

Principal Focus (F)

The point where parallel rays converge after passing through a converging lens, or the point from which they appear to diverge after passing through a diverging lens.

Focal Length

Distance from the optical center of a lens to its principal focus.

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Focal Plane

A plane perpendicular to the principal axis passing through the principal focus.

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Magnification

The ratio of the size of an image to the size of the object.

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Real Image

An image that can be projected onto a screen.

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Virtual Image

An image that cannot be projected onto a screen.

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Ray Diagrams for Convex Lens

Ray diagrams are used to determine the image's location, size, and characteristics when an object is placed in front of a convex lens.

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Object beyond 2F

When an object is placed farther than twice the focal length from a convex lens, the image is smaller and real.

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Object between 2F and F

Placing an object between twice the focal length and the focal length results in a larger, real, inverted image.

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Object within F

When an object is closer than the focal length, a virtual, upright, and larger image forms on the same side of the lens as the object.

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Lens Formula

Formula used to relate object distance, image distance, and focal length of a lens.

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Image Location (positive)

Distance measured in the same direction as the incident light is considered positive. A positive value indicates a real image.

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Image Location (negative)

A negative image distance indicates a virtual image.

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Focal Length & Angle of View

Longer focal lengths narrow the viewing angle and increase magnification; shorter focal lengths widen the angle and decrease magnification.

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Magnification (m)

Magnification compares the height of an image to the height of the object: m = image height / object height = image distance / object distance

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Ray Diagrams

Diagrams that trace the path of light to determine the location and characteristics of an image.

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Telescopes

Instruments that gather and focus light from distant objects, enabling greater magnification.

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Image Height vs Object Height

The ratio of image height to object height gives the magnification of the image.

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What happens to an image when the object is between the focal length and 2 times the focal length?

When an object is placed between the focal length (F) and twice the focal length (2F) of a convex lens, the image formed is larger than the object, real, and inverted.

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What happens to the image when the object is at a distance greater than 2 times the focal length?

When an object is placed at a distance greater than twice the focal length (2F) from a convex lens, the image formed is smaller than the object, real, and inverted.

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What happens to the image when the object is within the focal length?

When an object is placed closer than the focal length (F) to a convex lens, the image formed is virtual (cannot be projected), upright, and larger than the object.

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What are the four properties of image?

The four properties of an image formed by a lens are: (S) Size (smaller, larger, or same), (A) Attitude (inverted or upright), (L) Location (position relative to the lens), and (T) Type (real or virtual).

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What does positive image distance mean?

A positive image distance indicates that the image is real, which means it can be projected onto a screen.

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What does negative image distance mean?

A negative image distance indicates that the image is virtual, which means it cannot be projected onto a screen.

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How does a telescope work?

A telescope uses converging lenses or mirrors to collect and focus light from distant objects. The focused light creates a magnified image that can be observed.

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What is a ray diagram?

A ray diagram shows the path of light rays as they pass through lenses or mirrors. It helps determine the location, size, and type of image formed.

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What are the three principal rays in a ray diagram?

The three principal rays used in ray diagrams are: 1) A ray parallel to the principal axis that passes through the focal point after refraction. 2) A ray passing through the center of the lens that continues in a straight line. 3) A ray passing through the focal point that emerges parallel to the principal axis.

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Study Notes

Lenses

  • Lenses are classified as converging or diverging, based on their effect on parallel light rays.
  • Converging lenses (convex) cause parallel light rays to converge to a single point, while diverging lenses (concave) cause parallel light rays to spread out.
  • Lenses are composed of multiple prisms.

Objectives

  • Illustrate the effect of converging and diverging lenses on a beam of parallel rays.
  • Define principal axis, principal focus, focal length, focal plane, magnification, optical center.
  • Differentiate between real and virtual images.
  • Apply magnification equations.
  • Determine the focal length of a converging lens.

Mirrors vs. Lenses

  • Mirrors create images through reflection, while lenses create images through refraction.
  • Lenses are composed of multiple prisms that cause different amounts of deviation in light rays.

Types of Lenses

  • There are two basic types of lenses: converging (convex) and diverging (concave).
  • A converging lens focuses light rays to a point, while a diverging lens spreads light rays apart.

Anatomy of a Lens

  • Principal axis: A line passing through the center of the lens.
  • Optical center (center of lens): An imaginary point inside the lens where light rays pass without deflection.
  • Focal point (F): the point where parallel light rays converge after passing through a convex lens. The point from which diverging rays appear to originate when passing through a concave lens.
  • Focal length (f): The distance between the focal point and the optical center of the lens.

Object at Infinity

  • Object at infinity means the light rays coming from the object are considered parallel.

Focal Length

  • Focal length is the distance between the optical center of a lens and the focal point (for converging lenses) and the focus of diverging rays (for diverging lenses).
  • Longer focal length results in a narrower viewing angle and higher magnification.
  • Shorter focal length results in a wider viewing angle and lower magnification.
  • Focal length is measured in millimeters.

Uses of Lenses

  • Convex lenses are used in telescopes, microscopes, magnifying glasses, cameras, and projectors.
  • Concave lenses are used in peepholes, flashlights, and some types of corrective eyewear.

Real vs. Virtual Images

  • Real images can be projected onto a screen, while virtual images cannot.
  • Real images are inverted, while virtual images are upright.
  • Real images are located on the opposite side of the lens from the object, while virtual images are on the same side.

Magnification

  • Magnification (M): The ratio of the height of the image (h) to the height of the object (H).
  • Magnification is also equal to the ratio of the image distance (v) to the object distance (u).
  • A negative magnification value indicates an inverted image.

Lens Formula

  • 1/f = 1/u + 1/v, where f is the focal length, u is the object distance, and v is the image distance.
  • Distance measurements are taken from the optical center, with distances in the direction of the incident light ray considered positive.

Sign Conventions

  • Positive values are generally considered real and upright.
  • Negative values indicate virtual and inverted images.

Ray Diagrams

  • Ray diagrams trace the paths of light rays through a lens to determine the image location, size, and characteristics.
  • Using ray diagrams, you can determine whether the image is real/virtual, inverted/upright, smaller/larger and also the location of the image.

Constructing Ray Diagrams

  • There are three principal rays used in ray diagrams:
    • Ray 1: Parallel to the principal axis, refracts through the focal point.
    • Ray 2: Passes through the optical center, continues in a straight line.
    • Ray 3: Passes through the focal point, refracts parallel to the principal axis.

Drawing Ray Diagrams

  • When drawing a ray diagram to find an image, use two rays. Follow specific rules for drawing rays.
  • Apply learned rules to locate the image: size, position, real/virtual and upright/inverted.

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Related Documents

Lenses Lesson 19 (CSEC)

Description

This quiz covers the fundamental concepts of lenses, including their classification as converging and diverging types. You will explore the behavior of parallel light rays, key terms such as focal length and magnification, and the differences between real and virtual images. Test your knowledge of the principles of refraction and how lenses differ from mirrors.

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