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Questions and Answers
What is a form of energy that enables us to see?
What is a form of energy that enables us to see?
Light
Light travels in a curved path.
Light travels in a curved path.
False
Light travels at a speed of $3.0 imes 10^8$ msˉ¹ in a vacuum.
Light travels at a speed of $3.0 imes 10^8$ msˉ¹ in a vacuum.
True
What are some examples of luminous sources that emit light?
What are some examples of luminous sources that emit light?
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Our reflection in a mirror appears upside down.
Our reflection in a mirror appears upside down.
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The reflection you see in a plane mirror is a real image.
The reflection you see in a plane mirror is a real image.
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A real image is formed when light rays converge at a specific point.
A real image is formed when light rays converge at a specific point.
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The image in a plane mirror is laterally inverted.
The image in a plane mirror is laterally inverted.
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The ray that strikes a surface is called the [blank]
The ray that strikes a surface is called the [blank]
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The ray that bounces back off a surface is called the [blank]
The ray that bounces back off a surface is called the [blank]
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What is the line perpendicular to the reflecting surface at the point where the incoming ray strikes?
What is the line perpendicular to the reflecting surface at the point where the incoming ray strikes?
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The angle between the incident ray and the normal is called the [blank]
The angle between the incident ray and the normal is called the [blank]
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The angle between the reflected ray and the normal is called the [blank]
The angle between the reflected ray and the normal is called the [blank]
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Match the type of reflection with its description.
Match the type of reflection with its description.
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What type of surface produces a reflected image?
What type of surface produces a reflected image?
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What type of surface does not reflect an image because light is scattered in all directions?
What type of surface does not reflect an image because light is scattered in all directions?
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The angle of incidence is always greater than the angle of reflection.
The angle of incidence is always greater than the angle of reflection.
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The incident ray, the reflected ray, and the normal all lie in the same plane based on the laws of reflection.
The incident ray, the reflected ray, and the normal all lie in the same plane based on the laws of reflection.
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The bending of light as it passes from one medium to another is called refraction.
The bending of light as it passes from one medium to another is called refraction.
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What causes a pencil to appear bent when partially submerged in water?
What causes a pencil to appear bent when partially submerged in water?
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The speed of light is faster in a denser medium than in a less dense medium.
The speed of light is faster in a denser medium than in a less dense medium.
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When light travels from a less dense medium to a denser medium, it bends [blank] the normal.
When light travels from a less dense medium to a denser medium, it bends [blank] the normal.
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When light travels from a denser medium to a less dense medium, it bends [blank] the normal.
When light travels from a denser medium to a less dense medium, it bends [blank] the normal.
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What is the name for the ratio of the speed of light in a vacuum to the speed of light in a medium?
What is the name for the ratio of the speed of light in a vacuum to the speed of light in a medium?
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The higher the refractive index, the more the light will slow down when it enters a medium.
The higher the refractive index, the more the light will slow down when it enters a medium.
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Diamonds have a higher refractive index than glass.
Diamonds have a higher refractive index than glass.
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Lenses utilize reflection to form images.
Lenses utilize reflection to form images.
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Why do swimming pools and oceans appear shallower than they actually are?
Why do swimming pools and oceans appear shallower than they actually are?
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The speed of light in air is the same as the speed of light in a vacuum.
The speed of light in air is the same as the speed of light in a vacuum.
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What is the angle between the incidence ray and the normal called?
What is the angle between the incidence ray and the normal called?
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What is the angle between the reflected ray and the normal called?
What is the angle between the reflected ray and the normal called?
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What type of reflection occurs when parallel rays of light are reflected in a parallel direction?
What type of reflection occurs when parallel rays of light are reflected in a parallel direction?
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What type of reflection occurs when parallel rays of light are reflected in different directions?
What type of reflection occurs when parallel rays of light are reflected in different directions?
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The speed of light changes when it passes from one medium to another.
The speed of light changes when it passes from one medium to another.
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The change in the speed of light is not dependent on the material the light travels through.
The change in the speed of light is not dependent on the material the light travels through.
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What is the refractive index of a vacuum?
What is the refractive index of a vacuum?
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The refractive index of a material can be lower than 1.
The refractive index of a material can be lower than 1.
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Which of the following materials has the highest refractive index?
Which of the following materials has the highest refractive index?
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What is one common application of refraction?
What is one common application of refraction?
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Spectacles for people with defective vision are an example of the use of refraction.
Spectacles for people with defective vision are an example of the use of refraction.
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Where else is refraction applied in everyday life?
Where else is refraction applied in everyday life?
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Which of the following is NOT an example of a changing medium?
Which of the following is NOT an example of a changing medium?
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Study Notes
Unit 6: Light - Week 21
- Topic: Reflection and Refraction
Learning Objectives
- Students will be able to describe how light is reflected from a plane mirror.
- Students will be able to understand the laws of reflection.
- Students will be able to draw ray diagrams to show reflection of light.
- Students will be able to understand what refraction of light is.
Nature of Light
- Light is a form of energy that allows us to see.
- Light travels in a straight line.
- Light travels at a very high speed (3.0 x 108 ms-1) in a vacuum.
- Light is emitted by luminous sources such as the sun, stars, candles, lamps, etc.
Reflection of Light
- We often see our reflections in mirrors.
- A reflection in a flat mirror is upright, the same size, and the same color as the object.
- If an object moves closer to a mirror, its image moves closer. If an object moves away, its image moves away.
- A mirror reflection is virtual since there is nothing behind the mirror.
- Images projected onto a screen are real images.
- A reflection is laterally inverted.
Reflection of Light (1)
- The incoming ray is the ray that strikes the surface.
- The normal is a line perpendicular to the surface where the incoming ray hits it.
- The reflected ray is the ray that bounces off the surface.
- The angle of incidence is the angle between the incoming ray and the normal.
- The angle of reflection is the angle between the reflected ray and the normal.
Reflection of Light (2)
- The angle of incidence is equal to the angle of reflection (i = r).
- The incident ray, the reflected ray, and the normal to the surface of the mirror all lie in the same plane.
Types of Reflection
- Regular Reflection: Parallel incident rays reflect as parallel rays, creating a clear image (e.g., plane mirrors).
- Diffuse Reflection: Incident rays reflect in many directions, so no clear image is produced (e.g., most surfaces).
Laws of Reflection
- The angle of incidence is equal to the angle of reflection.
- The incident ray, the reflected ray, and the normal lie in the same plane.
How to Measure Angle of Incidence and Reflection
- Use a protractor to measure the angles of incidence and reflection.
- Position the incident ray, normal, and protractor on the drawing to measure the angles.
Making Measurements
- Detailed instructions on accurately measuring angles of incident and reflected rays. Use diagrams showing ray diagrams and protractor locations to aid measurement.
Refraction of Light
- A pencil placed partly in water appears bent or broken.
- Light changes direction when it passes from one transparent medium to another (e.g., air to water, air to glass).
- This bending is called refraction.
- Refraction happens at the boundary (interface) between the two media.
Angle of Incidence
- The angle between the normal and the incident ray that reaches the boundary.
Angle of Refraction
- The angle between the normal and the refracted ray on the other side of the boundary.
Refraction (From Air into Water/Glass)
- Light bends toward the normal when going from a less dense to a denser medium. (e.g., air to water, air to glass).
Refraction (From Water/Glass into Air)
- Light bends away from the normal when going from a denser to a less dense medium (e.g., water to air).
Why Does Refraction Happen?
- Light travels at different speeds in different materials (e.g., air, water, glass, diamond).
- The speed of light changes depending on the density of the material.
- Denser materials cause light to slow down more, resulting in greater refraction.
Application of Refraction
- Spoons appear bent when placed in water or other transparent liquids.
- Refraction is responsible for objects in water or other transparent materials appearing shallower than their actual depth.
- Refraction is used in lenses (e.g., eyeglasses, cameras) to focus light and form images.
- Refraction explains how peepholes, cameras, movie projectors, and telescopes work.
- Refraction explains why a pool looks shallower than it is.
Speed of Light and Refraction
- Light speed changes when moving between mediums.
- The amount of the speed change depends on the material.
- The refractive index is the ratio of the speed of light in vacuum to its speed in a medium.
Refractive Index
- Refractive index is unitless.
- The refractive index is higher for denser materials.
- The higher the refractive index, the more a light ray is bent.
Applications
- Lenses use refraction to form images for various purposes, including magnification.
- Eyeglasses use refraction to correct vision problems.
Concept Check Questions (with answers and diagrams)
- Include diagrams for clarity
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