Electromagnetic Waves and Light Production
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Questions and Answers

Which electromagnetic wave is primarily used in microwave ovens for heating food?

  • Radio waves
  • Infrared
  • Microwaves (correct)
  • Ultraviolet

What type of light production involves the emission of light due to the absorption of ultraviolet light, with a delayed emission?

  • Incandescence
  • Electric discharge
  • Phosphorescence (correct)
  • Fluorescence

In what context is chemiluminescence most suitable due to its minimal heat production?

  • Inside a standard light bulb
  • In a tanning booth
  • Near explosive materials (correct)
  • In a high-temperature industrial oven

Which type of electromagnetic wave is used in medical imaging?

<p>X-rays (C)</p> Signup and view all the answers

What form of light production relies on electricity passing through a gas?

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

Which application is NOT a use for ultraviolet radiation?

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

Which of the following scenarios would benefit most by using phosphorescence?

<p>An emergency exit sign during a power outage (D)</p> Signup and view all the answers

Which of the following electromagnetic waves has the shortest wavelengths?

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

According to the laws of reflection, what is the relationship between the angle of incidence and the angle of reflection?

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

Which of the following best describes specular reflection?

<p>Reflection of light from a smooth surface, with rays reflected in an uniform direction. (A)</p> Signup and view all the answers

If an incident ray strikes a plane mirror at an angle of 35° to the normal, what is the angle between the reflected ray and the mirror's surface?

<p>55° (A)</p> Signup and view all the answers

What is the speed of light in a material with a refractive index of 1.92, given the speed of light in a vacuum is approximately $3.00 \times 10^8$ m/s?

<p>$1.56 \times 10^8$ m/s (B)</p> Signup and view all the answers

What are the characteristics of an image formed by a concave mirror when an object is placed between the center of curvature (C) and the focal point (F)?

<p>Larger, Inverted, Beyond C, and Real (A)</p> Signup and view all the answers

When light travels from one transparent material to another, what phenomenon occurs besides refraction?

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

The critical angle is the angle of incidence that results in which type of refraction angle?

<p>90 degrees (B)</p> Signup and view all the answers

According to the content, when is no image produced by a concave mirror?

<p>When the object is at F. (B)</p> Signup and view all the answers

What is the phenomenon of refraction?

<p>The bending of light as it travels from one medium to another. (A)</p> Signup and view all the answers

Under what condition does total internal reflection occur?

<p>When the angle of incidence is greater than the critical angle going from slow to fast mediums (C)</p> Signup and view all the answers

If the critical angle for a plastic is 42 degrees, what would most likely happen to a light ray incident at 23 degrees?

<p>Partial reflection and refraction (C)</p> Signup and view all the answers

When light travels from air into glass, how does the refracted ray bend?

<p>The refracted ray bends towards the normal. (D)</p> Signup and view all the answers

Zircon has an index of refraction of 1.92. What does this value indicate?

<p>The speed of light in zircon is 1/1.92 times the speed of light in a vacuum. (D)</p> Signup and view all the answers

A convex lens is placed a distance 2F away from an object. Where is the created image, in relation to the lens and what are its basic characteristics?

<p>Same, Inverted, At 2F, and Real (D)</p> Signup and view all the answers

What is a primary use for convex mirrors due to their image characteristics?

<p>Increasing the field of view (A)</p> Signup and view all the answers

Flashcards

Electric Discharge

Production of light involving the passing of electric current through a gas.

Fluorescence

Immediate emission of light by absorbing ultraviolet light.

Incandescence

Production of light due to high temperatures.

Phosphorescence

Light is emitted over a long period of time because of absorption of ultraviolet light.

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Chemiluminescence

The production of light due to a chemical reaction, with little or no heat produced.

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Radio Waves

Electromagnetic waves that are used in AM/FM radio, TV signals, cellphone communication, radar, and astronomy.

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Microwaves

Electromagnetic waves that are used in telecommunications, microwave ovens, and astronomy.

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Ultraviolet Light

Electromagnetic waves that can cause skin to tan and sunburn, increase risk of skin cancer, stimulate production of vitamin D, kill bacteria, and are used in "black" lights.

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Laws of Reflection

The angle between the incident ray and the normal to the reflecting surface is always equal to the angle between the reflected ray and the normal.

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Specular Reflection

Reflection of light off a smooth, shiny surface where all reflected rays travel in the same direction.

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Diffuse Reflection

Reflection of light off a rough, irregular surface where reflected rays scatter in many directions.

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Refraction

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

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Index of Refraction (n)

The ratio of the speed of light in a vacuum to the speed of light in a given medium.

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Refraction: Air to Glass

When light travels from a less dense medium (like air) to a denser medium (like glass), it bends towards the normal.

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Refraction: Glass to Air

When light travels from a denser medium (like glass) to a less dense medium (like air), it bends away from the normal.

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Concave Mirror

A mirror that curves inward like the inside of a spoon.

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Speed of Light in a Medium

The speed of light in a medium is always less than the speed of light in a vacuum. The refractive index of a material is the ratio of the speed of light in a vacuum to the speed of light in that material. The speed of light in a material can be calculated using the following formula: v = c / n Where: v = the speed of light in the material c = the speed of light in a vacuum (3.00 x 10^8 m/s) n = the refractive index of the material

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Partial Reflection and Refraction

When light travels from one transparent medium to another, it is partially reflected and partially refracted. This means that some of the light bounces off the surface of the second medium, while the rest of the light passes through the surface and bends.

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Critical Angle

The critical angle is the angle of incidence at which light will be totally internally reflected when passing from a medium with a higher refractive index to a medium with a lower refractive index. This can only occur when light is travelling from a slower medium to a faster medium.

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Total Internal Reflection

Total internal reflection occurs when light traveling through a medium with a higher refractive index (denser medium) reaches the boundary with a medium with a lower refractive index (less dense medium) at an angle of incidence greater than the critical angle. This causes all of the light to be reflected back into the denser medium.

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Convex Mirror

A convex mirror is a curved mirror that bulges outwards. Its surface is curved outward and reflects light away from a focal point that is behind the mirror. This results in virtual, upright, and smaller images. Convex mirrors are used in security systems, vehicle side mirrors, and store checkout aisles because they allow for a wide field of view.

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Converging Lens

A lens is a transparent object that refracts light. A converging lens is thicker in the middle than at the edges. This type of lens causes parallel rays of light to converge at a focal point. The focal point is the point where the rays of light converge. The focal length is the distance from the center of the lens to the focal point.

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Real vs. Virtual Image

A real image can be projected onto a screen. It is formed by the actual intersection of light rays. A virtual image cannot be projected onto a screen. It is formed by the apparent intersection of light rays, but the rays do not actually converge.

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Image Characteristics: Converging Lens

The characteristics of an image formed by a lens depend on the object's position relative to the focal point and the type of lens. Images formed by a converging lens can be real or virtual, depending on the object's position. For example, when an object is placed beyond the focal point of a converging lens, a real, inverted, and smaller than object image forms behind the lens.

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Study Notes

Electromagnetic Waves and Applications

  • Radio waves are used for AM/FM radio, TV signals, cellphones, radar, and astronomy.
  • Microwaves are used in telecommunications, microwave ovens, and astronomy.
  • Infrared waves are used in remote controls, lasers, keeping food warm, and physical therapy.
  • Visible light is used in human vision, theatre/concert lighting, and rainbows.
  • Ultraviolet light causes tanning and sunburns, increases skin cancer risk, produces vitamin D, and kills bacteria.
  • X-rays are used for medical imaging, security equipment, and cancer treatment.
  • Gamma rays are used in cancer treatment and come from some nuclear decay.

Light Production Methods

  • Electric discharge produces light by passing electricity through a gas (e.g., neon signs).
  • Fluorescence produces light immediately by absorbing UV light (e.g., highlighters).
  • Incandescence produces light due to high temperatures (e.g., incandescent light bulbs).
  • Phosphorescence emits light over a long period after absorbing UV light (e.g., glow-in-the-dark stickers).
  • Chemiluminescence involves a chemical reaction that creates light without producing significant heat (e.g., glow sticks).

Light Production Scenarios

  • Near explosives: Chemiluminescence is best because it doesn't generate heat.
  • Entertainment venues: Chemiluminescence (glow sticks) or electric discharge (neon signs) are useful.
  • Underwater: Chemiluminescence or waterproof LED flashlights are suitable as they don't require electricity.

Laws of Reflection

  • The angle of incidence equals the angle of reflection.
  • The incident ray, reflected ray, and normal are in the same plane.

Specular vs. Diffuse Reflection

  • Specular reflection occurs from smooth, shiny surfaces.
  • Diffuse reflection occurs from dull, irregular surfaces.

Plane Mirror Reflection

  • If the angle of incidence is 35°, the angle of reflection is also 35°.
  • The angle between the mirror and the incident ray is 90° - 35° = 55°.

Ray Diagrams and Image Characteristics

  • Ray diagrams show how light reflects/refracts for object-mirror/lens systems.
  • Image characteristics (SALT) describe the image:
    • Size: Larger, smaller, or same size as the object.
    • Attitude: Upright or inverted.
    • Location: Relative to the mirror/lens.
    • Type: Real or virtual.

Concave Mirror Image Properties

Object Location Size Attitude Location Type
Beyond C Smaller Inverted Between C and F Real
At C Same Inverted At C Real
Between C & F Larger Inverted Beyond C Real
At F No image formed
Inside F Larger Upright Behind mirror Virtual

Refraction

  • Refraction is light bending when passing from one medium to another.
  • Light bends toward the normal when entering a denser medium.
  • Light bends away from the normal when entering a less dense medium.

Index of Refraction

  • A higher refractive index means slower light.
  • The index of refraction (n) relates speed of light (c) to the speed in the medium (v): n = c/v.

Partial Reflection and Refraction

  • Some light is reflected, some refracted when passing between transparent materials.

Critical Angle and Total Internal Reflection

  • The critical angle is the angle of incidence that produces a 90° angle of refraction.
  • Total internal reflection occurs when the angle of incidence exceeds the critical angle (light stays in the denser medium).

Lenses

  • Ray diagrams for lenses show how light refracts.

Convex Mirror Applications

  • Convex mirrors increase field of view, making them useful in security mirrors (stores, parking garages), and side mirrors on cars because a broader view of surroundings creates safety.

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SNC2D Exam Review Jan 2024 Physics Answers PDF

Description

Explore the fascinating world of electromagnetic waves and their applications, including uses of radio waves, microwaves, and X-rays. Additionally, learn about various methods of light production like electric discharge and fluorescence. Test your knowledge on how these concepts shape our daily lives.

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