geometric optics
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Questions and Answers

What fundamental principle does geometric optics primarily rely on?

  • The diffraction patterns produced by small openings
  • The rectilinear propagation of light (correct)
  • The principles of wave interference
  • The behavior of light as it bends through different media

According to the law of reflection, what must be true for an angle of incidence of a ray striking a surface?

  • It must equal the angle of reflection (correct)
  • It must be smaller than the angle of refraction
  • It has no relation to the angle of reflection
  • It is always greater than the angle of reflection

What phenomenon describes the separation of white light into its full spectrum of wavelengths?

  • Absorption
  • Transmission
  • Reflection
  • Dispersion (correct)

Why does sunlight appear slightly yellow instead of white?

<p>It is a mixture of all visible wavelengths with some excess yellow wavelengths. (A)</p> Signup and view all the answers

Which of the following describes a situation where light travels through matter?

<p>Light passing through a pane of glass (D)</p> Signup and view all the answers

When light is reflected off a mirror, what feature of the mirror is critical for producing clear images?

<p>The smoothness of the mirror's surface (B)</p> Signup and view all the answers

Which of the following describes the role of refraction in the formation of rainbows?

<p>It changes the direction of light based on wavelength. (D)</p> Signup and view all the answers

Which phenomenon would NOT be explained by geometric optics?

<p>The formation of halos around the sun due to ice crystals (A)</p> Signup and view all the answers

At what angle does red light (660 nm) refract when entering water from air at an incident angle of 75°?

<p>48° (A)</p> Signup and view all the answers

What is the primary effect of a convex lens on incoming parallel light rays?

<p>It converges them to a single focal point. (C)</p> Signup and view all the answers

What does the term 'ray' signify in geometric optics?

<p>A straight line originating from a light source (B)</p> Signup and view all the answers

Which of the following does NOT represent a way light can travel?

<p>Passing through a colloid (C)</p> Signup and view all the answers

Which color of light has the shortest wavelength and gets refracted the most through a prism?

<p>Violet (410 nm) (A)</p> Signup and view all the answers

What defines the interaction of light with smooth surfaces according to geometric optics?

<p>Light reflects uniformly and predictably (A)</p> Signup and view all the answers

Why is dispersion most spectacular against a dark background?

<p>Dark backgrounds enhance the contrast of colors. (C)</p> Signup and view all the answers

What must occur for dispersion to happen?

<p>Wavelengths must change direction differentially. (D)</p> Signup and view all the answers

What is one of the main benefits of optical fibers in medical procedures?

<p>They enable microsurgery with minimal incision. (D)</p> Signup and view all the answers

What is the purpose of the cladding material surrounding optical fibers?

<p>To prevent light from escaping the fiber. (D)</p> Signup and view all the answers

What characteristic of optical fibers allows them to transmit more conversations than copper conductors?

<p>High bandwidth. (C)</p> Signup and view all the answers

How is the index of refraction calculated for a medium with the speed of light at $2.012 \times 10^8$ m/s?

<p>By dividing the speed of light in vacuum by the speed of light in the medium. (C)</p> Signup and view all the answers

What results from light traveling from water to a gemstone at an angle of 80 degrees, resulting in an angle of refraction of 15.2 degrees?

<p>The gemstone's index of refraction is 5. (B)</p> Signup and view all the answers

What is the critical angle between glass and water if the index of refraction for glass is 1.5 and for water is 1.33?

<p>60 degrees (C)</p> Signup and view all the answers

How do optical signals in one fiber affect adjacent fibers?

<p>They do not produce undesirable effects. (A)</p> Signup and view all the answers

What is the significance of the transparency of optical fibers?

<p>It allows light to travel vast distances without requiring amplification. (D)</p> Signup and view all the answers

What is the characteristic of a virtual image produced by a diverging lens?

<p>The virtual image is located on the same side as the object. (A)</p> Signup and view all the answers

How is the magnification of a concave lens represented when the image is upright?

<p>m = +ve (B)</p> Signup and view all the answers

Where does the virtual image appear to originate when traced backward for a diverging lens?

<p>On the same side as the object (D)</p> Signup and view all the answers

Which statement correctly differentiates between real and virtual images?

<p>Real images can be projected on a screen. (C)</p> Signup and view all the answers

What happens to the light rays when producing a virtual image with a concave lens?

<p>They diverge and never meet. (C)</p> Signup and view all the answers

If the image distance (di) is negative for a lens system, what type of image is formed?

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

Which of the following describes the size of a virtual image compared to the object?

<p>It is always smaller than the object. (B)</p> Signup and view all the answers

What is the characteristic of magnification when |m| is equal to 1?

<p>The image is neither enlarged nor reduced. (C)</p> Signup and view all the answers

What type of image is produced by a concave lens?

<p>Virtual, upright, and smaller (A)</p> Signup and view all the answers

What is the power in diopters of a lens with a focal length of 50.0 mm?

<p>20 D (B)</p> Signup and view all the answers

What is the focal length of reading glasses that have a power of 1.75 D?

<p>0.57 meters (A)</p> Signup and view all the answers

If an object is placed 3.00 m from a camera lens with a focal length of 50.0 mm, how far must the film be placed from the lens?

<p>0.05 m (A)</p> Signup and view all the answers

What type of image is formed when an object is within the focal length of a convex lens?

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

What is the magnification of an object positioned 3.00 m away from a lens with a focal length of 50 mm?

<p>-0.0166 (D)</p> Signup and view all the answers

What kind of image does a concave mirror typically produce?

<p>Depends on the distance of the object (B)</p> Signup and view all the answers

Which type of mirror would likely produce a smaller image of an object?

<p>Convex mirror (A)</p> Signup and view all the answers

What happens to light rays reflected from a large concave mirror compared to a parabolic mirror?

<p>They do not cross at a single point. (C)</p> Signup and view all the answers

In what position does a virtual image appear when an object is placed between a concave mirror and its focal point?

<p>Behind the mirror. (D)</p> Signup and view all the answers

Which statement is true about the focal length of a convex mirror?

<p>It is always negative. (C)</p> Signup and view all the answers

What characteristic is unique to the image formed by a convex mirror?

<p>It is upright and diminished. (D)</p> Signup and view all the answers

What is the relationship between the radius of curvature and the focal length of a concave mirror?

<p>The focal length is half the radius of curvature. (C)</p> Signup and view all the answers

What type of image is produced by a concave mirror when the object is beyond the focal point?

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

Which of the following statements correctly describes the optical properties of parabolic mirrors compared to spherical mirrors?

<p>Parabolic mirrors have a well-defined focal point. (D)</p> Signup and view all the answers

If the object distance for a concave mirror is less than the focal length, what type of image is formed?

<p>A virtual and erect image. (B)</p> Signup and view all the answers

Flashcards

Geometric Optics

Branch of physics concerned with light's interaction with objects much larger than its wavelength, where light behaves like rays.

Light traveling from a source

Light can travel directly from a source, through mediums, or by reflection.

Ray

Straight line representing the direction of light travel.

Law of Reflection

Angle of incidence equals angle of reflection, measured relative to the surface normal.

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Surface Normal

A line perpendicular to the reflecting surface at the point of incidence.

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Angle of Incidence

Angle between the incident ray and the surface normal.

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Angle of Reflection

Angle between the reflected ray and the surface normal.

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Smooth surface reflection

Parallel rays hitting a smooth surface reflect in a single direction.

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Optical Fiber Cladding

A material surrounding the core of an optical fiber with a lower refractive index. It prevents light from escaping, guiding it along the fiber.

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Optical Fiber Low Loss

The property of optical fibers allowing light to travel long distances with minimal signal degradation.

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Optical Fiber High Bandwidth

The ability of optical fibers to transmit a large amount of data (e.g., numerous conversations) simultaneously.

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Optical Fiber Reduced Crosstalk

The property of optical fibers preventing interference between signals in adjacent fibers.

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Index of Refraction

A measure of how much light bends when entering a medium. It's the ratio of the speed of light in a vacuum to the speed of light in the medium.

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Critical Angle

The angle of incidence at which light traveling from a denser medium to a less dense medium is refracted at 90 degrees (grazing the surface).

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Refraction

The bending of light as it passes from one medium to another. It happens because light travels at different speeds in different media.

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Total Internal Reflection

The phenomenon where light traveling from a denser medium to a less dense medium is reflected back into the denser medium when the angle of incidence exceeds the critical angle.

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Converging Lens

A lens that causes parallel light rays to converge at a point, forming a real image.

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Diverging Lens

A lens that causes parallel light rays to spread out, forming a virtual image.

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Real Image

An image formed when light rays actually converge at a point, allowing the image to be projected onto a screen.

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Virtual Image

An image formed where light rays only appear to converge, but they don't actually meet, so the image cannot be projected.

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Magnification (m) for a converging lens

Magnification is the ratio of the image height to the object height. A positive magnification indicates an upright image.

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Magnification (m) for a diverging lens

Magnification is the ratio of the image height to the object height. A negative magnification indicates an inverted image.

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Focal Length

The distance between the lens center and the point where parallel light rays converge (for a converging lens) or diverge (for a diverging lens).

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Object Distance

The distance between the object and the lens.

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Dispersion

The spreading of white light into its full spectrum of wavelengths, caused by different wavelengths of light bending at different angles.

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Wavelength and Color

Each color of light corresponds to a specific wavelength. Pure wavelengths result in seeing only one color, while mixtures of wavelengths create other hues.

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How do rainbows form?

Rainbows are caused by the refraction and reflection of sunlight through water droplets. Different wavelengths are refracted at different angles, creating the visible spectrum.

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Focal Point

The point where parallel light rays converge after passing through a converging lens.

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Convex Lens

A lens that is thicker in the middle than at the edges, causing light rays to converge.

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Concave Lens Image

Concave (diverging) lenses always produce a virtual, upright, and smaller image on the same side of the lens as the object.

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Convex Lens Image (within focal length)

Convex (converging) lenses produce a virtual, upright, and enlarged image only when the object is within the focal length of the lens.

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Lens Power (Diopters)

Lens power is measured in diopters and is calculated as the reciprocal of the focal length in meters.

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Focal Length of Reading Glasses

The focal length of reading glasses can be calculated using the lens power in diopters.

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Real vs. Virtual Image

Real images are formed on the opposite side of the lens from the object and can be projected onto a screen, while virtual images are on the same side as the object and cannot be projected.

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Camera Film Distance

The distance between the lens and the film in a camera depends on the object's distance and the lens's focal length.

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Magnification (Lens)

Magnification is a ratio of image size to object size, calculated as -di/do where di is the image distance and do is the object distance.

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Dental Mirror Image

Dental mirrors are concave mirrors producing magnified virtual images.

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Concave mirror, virtual image?

When an object is placed between a concave mirror and its focal point, it produces a virtual image behind the mirror.

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Focal length of a concave mirror

The focal length of a concave mirror is positive because it's a converging mirror. A shorter focal length indicates a more strongly curved mirror and greater power.

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Why does a concave mirror not always have a well-defined focal point?

A large concave mirror's reflected rays don't converge at a single point, leading to an undefined focal point. To have a well-defined focal point, the mirror needs to be small compared to its radius of curvature.

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Convex mirror image

Convex mirrors always produce a virtual, upright, and smaller image behind the mirror, regardless of the object's position.

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What is the relationship between focal length and radius of curvature?

The focal length of a spherical mirror is half its radius of curvature: f = R/2.

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What happens to light rays reflected from a convex mirror?

Parallel rays of light reflected from a convex mirror appear to originate from a virtual focal point located at the focal distance behind the mirror.

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Convex mirror focal length?

Convex mirrors diverge light so they have a negative focal length. The smaller the radius of curvature, the smaller the focal length and the more powerful the mirror.

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Real image characteristic?

A real image is formed in front of the mirror when the object distance is greater than the focal length, and it can be projected onto a screen.

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Study Notes

Chapter 25: Geometric Optics

  • Optics is the branch of physics dealing with visible light and other electromagnetic waves.
  • Geometric optics focuses on the behavior of light when interacting with objects significantly larger than its wavelength. Light behaves as rays in this case.
  • Light travels in straight lines.
  • Light can travel from source to destination directly, through different mediums or by reflection (off a mirror).
  •  Geometric optics uses the law of reflection and refraction to predict light behavior.

Introduction

  • Light evokes spiritual emotions, such as when viewing a sunset or rainbow.
  • Geometric optics describes how light from a page or screen forms an image in the eye, similar to how a camera lens forms an image.

The Ray Aspect of Light

  • Light travels in three ways: directly through empty space, through various mediums (air, glass), or by reflection.
  • Light often travels in straight lines. Rays represent light, as straight lines originating from objects.

The Law of Reflection

  • The angle of incidence equals the angle of reflection.
  • Angles are measured relative to the perpendicular (normal) to the surface where the ray strikes the surface.
  • A smooth surface like a mirror reflects many parallel rays in a single direction.
  • Only observers at specific angles can see reflected light.

The Law of Refraction

  • The change in light's direction (bending) when passing through varying mediums is called refraction.
  • Refraction applies to lenses and other optical phenomena.
  • The speed of light in a material affects refraction, which is a central concept in Einstein's theory of relativity.
  • Speed of light is not dependant on the speed or direction of the source or observer.

The Speed of Light

  • The speed of light in a vacuum is a fundamental constant (approximately 3.00 x 10⁸ m/s).
  • Light travels slower through matter than in a vacuum, due to interactions with atoms and other material structures. This is quantifiable by the index of refraction.

Index of Refraction

  • The index of refraction (n) of a material is calculated by the ratio of the speed of light in a vacuum to its speed in that material.
  • Refraction depends on speed differences between mediums.
  • The index of refraction is always greater than or equal to 1.

Total Internal Reflection

  • Total internal reflection occurs when the incident angle is greater than the critical angle, causing all light to be reflected back into the first medium.
  • The critical angle depends on the refractive indices of the materials involved.
  • Total internal reflection is frequently used in optical fibers, where it ensures light propagation along the fiber.

Fiber Optics

  • Fiber optics transmits light through thin fibers of plastic or glass.
  • Light in the fiber is totally internally reflected due to the cladding's lower refractive index.
  • Fiber optics makes possible high-bandwidth data transmission and medical procedures.

Dispersion

  • Dispersion is the spreading of white light (a mixture of all wavelengths of visible light) into its constituent colors (spectrum) by mediums like prisms
  • Refraction varies depending on wavelengths, resulting in differing degrees of bending for different wavelengths.
  • Visible light is a mixture of all wavelengths, which separate into a spectrum when traveling through a prism
  •  Rainbows demonstrate dispersion via refraction and reflection of light as it interacts with water droplets in the atmosphere

Image Formation by Lenses (and mirrors)

  • Light rays converge (or appear to converge) to form an image.
  • Thin lenses (converging and diverging) have focal points and focal lengths.
  • Lenses with greater effect on light have larger power.
  • The power of a lens is the inverse of its focal length.
  •  The position and size of the image formed by a lens or mirror depend on the object position and the focal length of the optical component.
  • The magnification of the image (size of image relative to size of object) relates to the object and image distances and the focal length.

Ray Tracing

  • Ray tracing techniques are used to determine how light rays behave (refract or reflect) when passing through matter. This is used to find the image's position and magnification.
  • Different principles govern how different types of mirrors or lenses behave.

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