KS3 Physics - Light
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Questions and Answers

What effect does a prism have on white light?

  • It splits white light into its component colors. (correct)
  • It absorbs white light completely.
  • It reflects all colors equally.
  • It generates heat from white light.

Which color of light refracts the most when passing through a prism?

  • Red
  • Violet (correct)
  • Blue
  • Green

What happens when two primary colors of light are mixed in equal amounts?

  • They form a secondary color. (correct)
  • They emit energy as heat.
  • They produce a primary color.
  • They create white light.

What is the outcome when an object appears white?

<p>It reflects all colors of light. (B)</p> Signup and view all the answers

Why do red surfaces appear red?

<p>They reflect red light and absorb all others. (C)</p> Signup and view all the answers

Which of the following statements about black objects is correct?

<p>They absorb all light and reflect none. (D)</p> Signup and view all the answers

What results from mixing all three primary colors of light in equal measures?

<p>White light (D)</p> Signup and view all the answers

What color is NOT considered a primary color of light?

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

What color will a red object appear when viewed through a red filter?

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

Which of the following statements is true about colored filters?

<p>They only transmit their own color and absorb others. (A)</p> Signup and view all the answers

If a white object is viewed through a red filter, what will be its appearance?

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

What happens to a green object viewed through a red filter?

<p>It appears black. (D)</p> Signup and view all the answers

Under exclusively red light, how will a white object appear?

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

Which scenario correctly describes the transmission of yellow light through filters?

<p>It passes through both red and green filters. (B)</p> Signup and view all the answers

Which of the following locations is least likely to utilize colored filters?

<p>Solar energy plants (D)</p> Signup and view all the answers

When viewing an object under colored light that is different from its color, how will the object appear?

<p>It absorbs all light and appears black. (C)</p> Signup and view all the answers

What characteristic distinguishes the image seen in a plane mirror from a real image?

<p>The image is laterally inverted. (D)</p> Signup and view all the answers

What method can be used to locate the position of a virtual image in a plane mirror?

<p>Draw the virtual rays and find where they intersect. (B)</p> Signup and view all the answers

Why is the image formed by a plane mirror classified as a virtual image?

<p>It appears to be generated by rays that do not actually converge. (C)</p> Signup and view all the answers

What happens to the size and orientation of images formed by real images when compared to their objects?

<p>They are smaller and inverted. (B)</p> Signup and view all the answers

What is the primary function of a convex mirror?

<p>To provide a wide field of view for safety. (B)</p> Signup and view all the answers

When light rays are reflected off a concave mirror, what is the typical outcome regarding the image formed?

<p>The image can be real or virtual depending on the distance. (C)</p> Signup and view all the answers

What is the significance of normal lines when drawing light rays for locating images in mirrors?

<p>They help indicate the angle of incidence. (C)</p> Signup and view all the answers

Which property does not apply to the images created by curved mirrors?

<p>Images are always the same size as the object. (C)</p> Signup and view all the answers

What is the primary effect of using a convex mirror?

<p>It magnifies images while creating virtual images. (C)</p> Signup and view all the answers

In what situation will a concave mirror form a virtual image?

<p>When the object is between the focal point and the mirror. (B)</p> Signup and view all the answers

How does the curvature of a concave mirror affect the focal point?

<p>It moves the focal point closer to the mirror. (A)</p> Signup and view all the answers

What does the phenomenon of refraction explain regarding light?

<p>Light bends due to variation in optical density of materials. (C)</p> Signup and view all the answers

Which of the following describes a real-world application of concave mirrors?

<p>They are used in solar furnaces. (D)</p> Signup and view all the answers

What is the effect of light entering water on the appearance of a straw?

<p>The straw seems broken at the surface. (D)</p> Signup and view all the answers

What is a characteristic of concave mirrors compared to convex mirrors?

<p>Concave mirrors can focus light to create real images. (A)</p> Signup and view all the answers

What does an increase in optical density of a medium typically do to the speed of light?

<p>Decreases the speed of light. (B)</p> Signup and view all the answers

What defines the refractive index of a material?

<p>The ratio of the speed of light in a vacuum to the speed of light in the medium. (B)</p> Signup and view all the answers

During refraction, what happens to light as it moves from a denser medium to a less dense medium?

<p>Light speeds up and bends away from the normal. (A)</p> Signup and view all the answers

Which of the following correctly describes total internal reflection (TIR)?

<p>It occurs when the angle of incidence exceeds the critical angle. (C)</p> Signup and view all the answers

How does the critical angle relate to the refractive index of a substance?

<p>The higher the refractive index, the smaller the critical angle. (C)</p> Signup and view all the answers

Which of the following applications is NOT associated with total internal reflection?

<p>Concave mirrors. (B)</p> Signup and view all the answers

What factor primarily determines whether light will refract or reflect when it meets a boundary between two media?

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

Which statement best describes how optical fibers utilize total internal reflection?

<p>They work by having a core and cladding with different refractive indices. (B)</p> Signup and view all the answers

What happens to the angle of refraction as the angle of incidence increases when entering a more optically dense medium?

<p>The angle of refraction increases until TIR occurs. (D)</p> Signup and view all the answers

What happens to light when it passes from air into glass?

<p>It slows down and bends towards the normal line. (C)</p> Signup and view all the answers

Which statements correctly describe the angles related to refraction when light passes through glass?

<p>Angles in air are equal (i = y) and angles in glass are equal (r = x). (D)</p> Signup and view all the answers

What is the relationship between a substance's refractive index and its optical density?

<p>Higher refractive index signifies greater optical density. (C)</p> Signup and view all the answers

When light exits glass back to air, which of the following occurs?

<p>The speed of light increases, bending away from the normal. (D)</p> Signup and view all the answers

In a refraction experiment, what is observed regarding the angles as the light passes through a transparent block?

<p>The angle decreases when entering and increases when exiting. (D)</p> Signup and view all the answers

Why does light bend more in materials with higher refractive indices?

<p>They change the speed of light significantly. (D)</p> Signup and view all the answers

What role does the normal line play in the process of refraction?

<p>It divides the angles of incidence and refraction. (A)</p> Signup and view all the answers

What is the expected relationship between the angles of incidence and emergence in a basic refraction scenario?

<p>The angle of incidence and emergence are always equal. (B)</p> Signup and view all the answers

Flashcards

Dispersion of light

The process of separating white light into its component colours.

Prism

A triangular block of glass used to separate white light into its spectrum.

Spectrum of light

The range of colours produced when white light is separated, typically ROY G. BIV.

Refraction

The bending of light as it passes from one medium to another.

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Primary colours of light

Red, green, and blue; mixing these in varying amounts produces all visible colours

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Secondary colours of light

Magenta, yellow, and cyan; created by mixing two primary colours in equal amounts

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White object

Reflects all colours of light.

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Black object

Absorbs all colours of light; reflects none.

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Light reflection and color

An object's color depends on the wavelengths of light it reflects. If red light is the only light present, a white object will reflect only red light and appear red. If no light is reflected, the object appears black.

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Colored object under colored light

When the light color matches the object's color, the object appears that color. Otherwise, no light is reflected, appearing black.

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Light filter

A filter that allows only one specific color of light to pass through, absorbing all other colors.

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Red filter

A red filter transmits only red light; all other colors are absorbed.

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White object through red filter

Appears red because only red light is transmitted and reflected.

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Green object through red filter

Appears black because no green light is transmitted through the red filter; so it won't reflect any.

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Yellow light composition

Yellow light is made of red and green light.

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Light filter applications

Light filters are used in theatre and photography to obtain different lighting effects (e.g., create certain moods).

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Virtual Image

An image that appears to be located behind a mirror, but light rays do not actually pass through it.

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Real Image

An image that is formed when light rays actually converge at a point.

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Lateral Inversion

The sideways flipping of an image in a plane mirror.

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Plane Mirror

A flat mirror that creates a virtual image.

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Convex Mirror

A curved mirror that curves outwards; used for wider viewing angles.

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Concave Mirror

A curved mirror that curves inwards; can magnify images.

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Locating a reflected image

Drawing light rays reflecting off a mirror and tracing them back to find the image's location.

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Virtual rays

Extrapolated lines representing the path light rays appear to take in a virtual image formation.

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What does a convex mirror do to light?

A convex mirror spreads light rays further apart, causing them to diverge. This means the rays seem to originate from a point behind the mirror.

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What kind of image does a convex mirror produce?

Convex mirrors always produce virtual images, which means the image appears behind the mirror and cannot be projected onto a screen.

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How does the curvature of a convex mirror affect its focal point?

A more curved convex mirror has a shorter focal length, meaning the focal point is closer to the mirror. This results in greater divergence of light rays.

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What does a concave mirror do to light?

A concave mirror converges incoming light rays, bringing them together at a focal point.

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What types of images can a concave mirror produce?

Depending on the object's position relative to the focal point, a concave mirror can produce both real and virtual images.

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How does the curvature of a concave mirror affect its focal point?

A more curved concave mirror has a shorter focal length, placing the focal point closer to the mirror. This leads to greater convergence of light rays.

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What is refraction?

Refraction is the bending of light as it passes from one medium to another, such as from air to water or water to glass.

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What causes refraction?

Light travels at different speeds in different mediums. This difference in speed causes the light to change direction, resulting in refraction.

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Why does refraction occur?

Refraction happens because light travels at different speeds in different materials. When light enters a denser medium, it slows down, causing it to bend towards the normal line. When it exits a denser medium, it speeds up, bending away from the normal.

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Normal line

The normal line is an imaginary line perpendicular to the surface at the point where light enters or exits the medium. It's a reference line used to measure angles in refraction.

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Angle of incidence

The angle of incidence is the angle between the incident ray (light entering the medium) and the normal line.

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Angle of refraction

The angle of refraction is the angle between the refracted ray (light traveling within the medium) and the normal line.

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Refractive index

The refractive index is a measure of how much light bends when it passes from one medium to another. A higher refractive index means the material is more optically dense, causing greater bending.

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What happens when light travels from a less dense to a more dense medium?

When light travels from a less dense medium to a more dense medium (e.g., from air to water), it bends towards the normal line because it slows down.

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What happens when light travels from a more dense to a less dense medium?

When light travels from a more dense medium to a less dense medium (e.g., from water to air), it bends away from the normal line because it speeds up.

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Refraction: Density & Bending

Light bends when moving from one medium to another because its speed changes. This change in speed is related to the optical density of the materials - denser materials slow down light more, causing a greater bend.

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Refraction: Problems

Refraction can cause problems by distorting images, blurring vision, and hindering communication signals.

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Refraction: Applications

Refraction has various applications, such as lenses in cameras and eyeglasses, fiber optic cables for fast communication, and prisms for separating light into its colors.

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Total Internal Reflection (TIR)

When light traveling from a denser medium to a less dense medium hits the interface at an angle greater than the critical angle, it reflects back inside the denser medium.

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Critical Angle

The minimum angle of incidence at which total internal reflection occurs. It depends on the refractive indices of the two mediums.

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Optical Fiber: TIR

Optical fibers use total internal reflection to transmit signals over long distances. Light bounces off the fiber's internal surface, minimizing signal loss.

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Uses of Optical Fibers

Optical fibers are used in telecommunications, medicine, and other fields for high-speed data transmission, endoscope imaging, and various sensing applications.

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Study Notes

KS3 Physics - Light

  • Light is a form of energy that travels in straight lines.
  • Luminous objects produce their own light.
  • Non-luminous objects reflect light from a source.
  • Light can be reflected, absorbed, or transmitted.
  • Transparent materials allow light to pass through easily.
  • Translucent materials allow some light to pass through but scatter it.
  • Opaque materials do not allow light to pass through.
  • Light travels at different speeds in different materials.
  • The speed of light changes when it passes from one medium to another.
  • Refraction is the bending of light as it passes from one medium to another.
  • Total internal reflection (TIR) occurs when light travelling from denser to less dense medium hits an interface at an angle greater than the critical angle.

Luminous vs Non-luminous objects

  • Luminous objects produce their own light, like light bulbs, candles, or the Sun.
  • Non-luminous objects reflect light from a source, such as a mirror, a book, or a person.

Types of Objects

  • Transparent: Objects that allow light to pass through them completely (e.g., glass, clear plastic).
  • Translucent: Objects that allow some light to pass through, but scatter it, creating a blurry image (e.g., frosted glass, wax paper).
  • Opaque: Objects that do not allow any light to pass through them (e.g., wood, metal, brick).

The Pinhole Camera

  • A pinhole camera creates an inverted image of a light source.
  • The image in a pinhole camera is formed by light rays travelling in straight lines.

The Eye and the Camera

  • The eye and a camera work in similar ways
  • Both have an aperture (pupil in the eye and the camera lens opening), to let light in.
  • Both have a lens to focus light onto a light-sensitive surface (retina in the eye and film, or a digital sensor in the camera).

Coloured Light and Coloured Filters

  • White light is a mixture of colours.
  • A prism can separate these colours.
  • Coloured objects reflect some colours of light and absorb other colours.
  • Coloured filters only allow certain colours of light to pass through.
  • Different colours are reflected and absorbed differently.

The Law of Reflection

  • The angle of incidence is equal to the angle of reflection.
  • The normal line is a line perpendicular to the reflecting surface.

Curved Mirrors

  • Convex mirrors spread light rays apart, making the reflected image smaller and farther away.
  • Concave mirrors make the light rays converge.

Refraction

  • Light changes direction when travelling through different mediums like air and water.
  • The amount of bending depends on the refractive index.
  • Refractive index is the ratio of the speed of light in a vacuum to the speed of light in that substance.
  • Swimming pools appear shallower than they really are due to refraction;
  • Things look different under water due to refractive index changes.

Total Internal Reflection

  • Total internal reflection occurs when light travels from a denser medium to a less dense medium at an angle greater than the critical angle, it will entirely reflect.
  • Optical fibres use TIR to transmit light.
  • TIR is important in endoscopes and telecommunications.

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KS3 Physics - Light - Lessons 1-2 - PDF

Description

Explore the fundamental concepts of light in this KS3 Physics quiz. Learn about luminous and non-luminous objects, the properties of light, and the principles of reflection, refraction, and total internal reflection. Test your understanding of how light interacts with different materials.

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