Physics Chapter: Light Reflection and Refraction

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Questions and Answers

What phenomenon describes the bending of light when it passes through a small opening or around an obstacle?

  • Refraction
  • Dispersion
  • Reflection
  • Diffraction (correct)

In the context of light, what does the straight-line propagation of light imply about its behavior?

  • Light can only travel through transparent materials.
  • Light travels in straight lines unless obstructed or diffracted. (correct)
  • Light is always visible regardless of the medium.
  • Light can travel at varying speeds in different mediums.

Which theory postulated in the 20th century suggested that light exhibits both particle and wave characteristics?

  • Electromagnetic Theory
  • Newtonian Optics
  • Classical Wave Theory
  • Quantum Theory of Light (correct)

What property of light allows a highly polished surface to reflect most of the light that strikes it?

<p>Specular reflection (D)</p> Signup and view all the answers

What primarily causes the formation of a shadow when a light source is obstructed by an opaque object?

<p>The straight-line propagation of light (C)</p> Signup and view all the answers

What is the relationship between the angle of incidence and the angle of reflection in all types of reflecting surfaces?

<p>The angle of incidence is equal to the angle of reflection. (D)</p> Signup and view all the answers

In a concave mirror, where is the center of curvature located relative to the mirror?

<p>It lies in front of the mirror. (C)</p> Signup and view all the answers

A concave mirror produces a magnified, real image of an object placed 10 cm in front of it. This implies that the image distance (v) is:

<p>30 cm (D)</p> Signup and view all the answers

What happens to parallel rays of light when they strike a convex mirror?

<p>They diverge and appear to come from a point on the principal axis. (D)</p> Signup and view all the answers

A convex mirror of focal length 10 cm is used as a rearview mirror in a car. An object is placed 100 cm from the mirror. What is the magnification of the image?

<p>0.1 (C)</p> Signup and view all the answers

Which of the following correctly defines the focal length of a spherical mirror?

<p>It is half the distance between the pole and the principal focus. (A)</p> Signup and view all the answers

An object is placed at a distance of 20 cm from a concave mirror. The image formed is inverted and half the size of the object. What is the focal length of the mirror?

<p>10 cm (D)</p> Signup and view all the answers

When the reflecting surface of a mirror is curved inwards, what type of mirror is it classified as?

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

Consider two spherical mirrors, one concave and one convex, each with the same focal length. An object is placed at a distance of 2f from each mirror. The nature of the image formed in each case is:

<p>Real and inverted for concave, virtual and upright for convex (C)</p> Signup and view all the answers

A small object is placed 20 cm in front of a concave mirror. The image formed is twice the size of the object. What is the radius of curvature of the mirror?

<p>40 cm (D)</p> Signup and view all the answers

A convex mirror of focal length 10 cm is used to form the image of an object placed at a distance of 5 cm from the mirror. Where will the image be formed?

<p>2.5 cm behind the mirror (C)</p> Signup and view all the answers

A concave mirror produces a real and inverted image twice the size of the object. If the object distance is 20 cm, what is the image distance?

<p>-40 cm (C)</p> Signup and view all the answers

A concave mirror forms a virtual image of an object placed at (1/3^rd) of its focal length. What is the magnification of the image?

<p>3 (A)</p> Signup and view all the answers

A concave mirror forms an image of an object placed at 15 cm in front of it. If the image is formed at 30 cm in front of the mirror, what is the focal length of the mirror?

<p>10 cm (B)</p> Signup and view all the answers

A person stands 2 m from a convex mirror. If the radius of curvature of the mirror is 4 m, what is the magnification of the image?

<p>0.5 (B)</p> Signup and view all the answers

What is the relationship between the radius of curvature R and the focal length f for spherical mirrors?

<p>R = 2f (A)</p> Signup and view all the answers

When an object is placed at infinity in front of a concave mirror, what is the nature and size of the image formed?

<p>Highly diminished and real (C)</p> Signup and view all the answers

What happens to the image when an object is placed between the pole P and the focus F of a concave mirror?

<p>It is virtual and erect (C)</p> Signup and view all the answers

Which of the following statements about ray diagrams for concave mirrors is incorrect?

<p>A ray that strikes the mirror perpendicularly is reflected at a 45-degree angle. (B)</p> Signup and view all the answers

If a concave mirror forms a real image, which position of the object would likely not yield an image on a screen?

<p>At the focus F (C)</p> Signup and view all the answers

For the image formed by a concave mirror to be real, where must the object be placed?

<p>Between F and C (D)</p> Signup and view all the answers

What happens to a light ray as it travels from a rarer medium to a denser medium?

<p>It bends towards the normal. (A)</p> Signup and view all the answers

When observing the line under a glass slab at an angle, what effect is most likely observed?

<p>The line appears bent at the edges. (A)</p> Signup and view all the answers

Why does a light ray emerge parallel to the incident ray after passing through a rectangular glass slab?

<p>Because bending at one surface cancels bending at the other. (C)</p> Signup and view all the answers

Which statement correctly describes the refractive index?

<p>It relates to the speeds of light in different media. (A)</p> Signup and view all the answers

Which of the following statements regarding Snell's law of refraction is true?

<p>The incident ray, refracted ray, and normal lie in the same plane. (D)</p> Signup and view all the answers

If the angle of incidence is equal to zero, what happens to the light ray at the interface of two media?

<p>It passes straight through without bending. (D)</p> Signup and view all the answers

What is the main use of concave mirrors in torches and headlights?

<p>To create powerful parallel beams of light (A)</p> Signup and view all the answers

What characteristic describes the image formed by a convex mirror when the object is located at a finite distance?

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

What will happen to the image of an object in a convex mirror if the object is moved farther away?

<p>The image becomes smaller and appears further away (C)</p> Signup and view all the answers

In the New Cartesian Sign Convention for spherical mirrors, how is the distance measured to the left of the origin characterized?

<p>As negative (A)</p> Signup and view all the answers

Which type of mirror produces a full image of a large object, such as a tall tree?

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

Why do dentists prefer using concave mirrors?

<p>They magnify the image of the teeth (B)</p> Signup and view all the answers

What is a characteristic of the images formed by plane mirrors regardless of the object's distance?

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

What is the focal length of a concave mirror if its radius of curvature is 40 cm?

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

Flashcards

How do we see objects?

We see objects when light reflects off them into our eyes.

Transparent medium

A material that allows light to pass through, making objects behind it visible.

Ray of light

A straight-line path along which light travels.

Diffraction of light

The bending of light around small obstacles, showing light's wave nature.

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Reflection of light

The bouncing back of light from a polished surface, like a mirror.

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Laws of Reflection

The angle of incidence equals the angle of reflection; all rays lie in the same plane.

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Plane Mirror Image Properties

Virtual, erect, same size as the object, laterally inverted, and equidistant from the mirror.

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Concave Mirror

A mirror curved inwards, focusing light to a point in front of it.

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Convex Mirror

A mirror curved outwards, where light rays diverge and appear to come from a point behind it.

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Principal Focus

The point where light rays converge in a concave mirror or appear to diverge from in a convex mirror.

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Image Formation by Concave Mirror

The creation of images through reflection in a concave mirror based on object position.

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Image Properties of Convex Mirror

Images formed by a convex mirror are virtual, erect, and diminished.

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Sign Convention for Spherical Mirrors

Rules used to define positive and negative distances in mirror formulas.

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Magnification in Mirrors

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

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Uses of Convex Mirrors

Commonly used in vehicles for rear-view mirrors, providing wider field of view.

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Radius of curvature (R)

The distance from the mirror's surface to its center of curvature.

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Focal length (f)

The distance from the mirror's surface to the focal point, where light converges or appears to diverge.

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Relationship between R and f

For spherical mirrors, the radius of curvature R is twice the focal length f (R = 2f).

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Principal focus (F)

The point where parallel rays of light either converge or seem to diverge after reflecting from the mirror.

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Ray diagrams for image location

Diagrams used to trace light rays to determine the position and nature of an image formed by a mirror.

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Glass Slab Experiment

An experiment demonstrating refraction by observing a line under a glass slab.

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Angle of Incidence

The angle between the incident ray and the normal at the point of incidence.

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Angle of Refraction

The angle between the refracted ray and the normal after bending.

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Snell's Law

The ratio of sine of angle of incidence to sine of angle of refraction is constant for given media.

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Refractive Index

A measure of how much light slows down in a medium compared to vacuum.

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Image Distance (v)

The distance of the image from the pole of the mirror.

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Mirror Formula

The relationship between object distance (u), image distance (v), and focal length (f): 1/f = 1/v + 1/u.

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Magnification (m)

The ratio of the height of the image to the height of the object, indicating how much larger or smaller the image is.

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Relation of Magnification to distances

Magnification (m) can also be expressed as m = -v / u.

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Positive Magnification

Indicates that the image is virtual and erect.

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Negative Magnification

Indicates that the image is real and inverted.

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New Cartesian Sign Convention

A system of signs used to define distances and orientations in mirror formulas.

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Study Notes

Light: Reflection and Refraction

  • Light is needed for us to see objects
  • Objects reflect light falling on them, allowing us to see them
  • Light passes through transparent objects
  • Light travels in straight lines, demonstrated by shadows
  • Diffraction occurs when light bends around small objects
  • Light exhibits wave-like and particle-like properties (explained in higher levels)
  • Modern quantum theory unites wave- and particle-like behaviors

Reflection of Light

  • Highly polished surfaces (mirrors) reflect most light
  • Laws of reflection:
    • Angle of incidence equals angle of reflection
    • Incident ray, normal, and reflected ray lie in the same plane
  • Plane mirrors produce virtual, erect images of same size as the object
  • Images are as far behind the mirror as the object is in front
  • Images are laterally inverted

Spherical Mirrors

  • Reflecting surface of spherical mirrors can curve inwards (concave) or outwards (convex)
  • Concave: Reflecting surface faces inward, center of sphere (used in torches and search lights)
  • Convex: Reflecting surface curves outward (used as rear-view mirrors)
  • Pole (P): Centre of the reflecting spherical surface (lies on the surface)
  • Centre of Curvature (C): Centre of the sphere the reflecting surface forms part of (lies outside the surface)
  • Radius of Curvature (R): Distance between the pole and the centre of curvature (R=2f)
  • Principal Axis: Line passing through pole and centre of curvature (perpendicular to the mirror at the pole).
  • Aperture: Diameter of the reflecting surface
  • Focal Length (f): Distance between the pole and the principal focus (f = R/2)
  • Principal Focus: Point where reflected parallel rays converge (concave) or appear to diverge from (convex)

Image Formation by Spherical Mirrors

  • Concave Mirrors:
    • Image characteristics (position, size and nature) depend on object position relative to F, C and P
    • Image can be real (inverted) or virtual (erect)
    • Image can be magnified, diminished or same size
  • Convex Mirrors:
    • Always produce virtual, erect, diminished images
    • Image is behind the mirror, smaller than the object

Image Formation Using Ray Diagrams

  • Methods for locating image positions including: -A ray parallel to the principal axis reflects through the focus (concave) or appears to diverge from it (convex)
    • A ray through the focus reflects parallel to the principal axis (concave) or heading toward the focus (convex) -A ray through the center of curvature reflects back along the same path

Uses of Spherical Mirrors

  • Concave: Torches, headlights, shaving mirrors, dental instruments, solar furnaces
  • Convex: Rear-view mirrors in vehicles

Refraction of Light

  • Light changes direction when entering a different medium (e.g., from air to water)
  • This is called refraction.
  • Refraction occurs because different media affect the speed of light
  • Refraction is described by Snell's Law (ratio of sines of incidence and refraction is constant, for given light and media)

Refractive Index

  • Ratio of speed of light in a medium to the speed of light in a vacuum (or air)
  • Optically denser medium has a higher refractive index

Refraction through a Rectangular Glass Slab

  • Light bends towards the normal when entering a denser medium and away from the normal when exiting
  • Emergent ray is parallel to the incident ray but is shifted slightly.
  • The refractive index relates to the speed of light in different media

Refraction by Spherical Lenses

  • Lenses are transparent materials bound by one or more spherical surfaces.
  • Convex lenses converge light (converging lenses)
  • Concave lenses diverge light (diverging lenses)
  • Key lens parts are:
    • Optical center: Center point on a lens through which light passes without deflection
    • Principal axis: Line through the centers of curvature
    • Principal foci: Points where parallel light rays converge (convex) or seem to diverge (concave)

Image Formation by Lenses

  • Convex and concave lenses produce different image characteristics based object position and focal length.
    • Convex lens : Image can be real (inverted) or virtual (erect) and can be magnified, diminished, or same size as the object.
    • Concave lens: Always produces virtual, erect, and diminished images.

Sign Conventions

  • New Cartesian Sign Convention uses a consistent system for defining positive and negative distances for object and image positions related to the principal axis.

Mirror and Lens Formulas

  • Mirror Formula: 1/u + 1/v = 1/f
  • Magnification Formula (Mirrors and Lenses): m = -v/u = h'/h

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