Physics: Electromagnetic Waves

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What is the ratio of the sines of the angle of incidence and the angle of refraction relative to the normal to the surface?

Equal to the inverse ratio of the 2 indices of refraction

What is the main reason for the dispersion of white light into its component colors?

The different wavelengths of the component colors

What is the order of the colors of the visible spectrum, from longest to shortest wavelength?

Red, orange, yellow, green, blue, violet

What is the speed of light in a vacuum?

The same for all colors of light

What is a prism, in the context of light dispersion?

A transparent glass with 2 flat surfaces angled at an angle

What is the primary characteristic of electromagnetic waves?

They travel through empty space and are mostly invisible

What is the relationship between wavelength and frequency in the electromagnetic spectrum?

Wavelength and frequency have an inversely proportional relationship

What type of wave is characterized by particle motion parallel to the energy motion?

Longitudinal wave

What is the primary difference between mechanical and non-mechanical waves?

Mechanical waves require a medium, while non-mechanical waves do not

What is the law that describes the relationship between the incident ray, reflected ray, and the normal in reflection?

The Reflection Law

What is the term for the reflection of light from a smooth surface?

Specular reflection

What is the term for the bending of light as it passes from one medium to another?

Refraction

What is the primary characteristic of electromagnetic waves in terms of their particle motion?

They are transverse waves

What is the term for the angle at which light is incident on a surface?

Incidence angle

What is the term for the ratio of light speed in free space to the speed in a given medium?

Refractive index

What is the reason for dispersion of white light into 7 colors when it passes through a glass prism?

because different colors of light bend at different angles due to differences in velocity

What is the physical quantity that measures the tendency of a material to slow down light as it travels through it?

Optical density

What is the shape of a concave mirror?

Spherical

What is the direction of the center of curvature and focal point of a convex mirror?

On the far side of the mirror

What is the purpose of the mirror equation?

To provide numerical information about image distance and object size

What happens to light rays when they reflect from a convex mirror?

They diverge

What is the significance of the focal length of a concave mirror?

It is the point where incident rays parallel to the principal axis pass through

What is the relationship between the frequency of light and the resonant frequency of electrons in a material?

The frequency of light matches the resonant frequency of electrons

What is the purpose of a ray diagram for concave mirrors?

To help determine the approximate location and size of the image

What do negative values for image distance indicate in mirror equation?

Image is located behind the mirror

What is the angle of deviation in the context of light refraction?

The angle between the incident ray and the refracted ray

What happens to an incident ray that passes through the center of a converging lens?

It continues in the same direction it had when it entered the lens

What type of image is formed when light rays are converging to a point after refracting through a lens?

Real image

What is the characteristic of the image formed by a diverging lens?

Virtual and upright

What happens to an incident ray that travels parallel to the principal axis of a converging lens?

It refracts through the lens and converges to a point

What is the characteristic of the image formed when an object is located in front of a focal point of a converging lens?

Virtual and reduced in size

Study Notes

Mirror Equation

  • Negative values for image distance indicate image is located behind the mirror
  • Negative/positive sign in front of numerical value for physical quantity represents info about direction
  • In case of image distance, negative value always indicates existence of virtual image located behind mirror
  • In case of image height, a positive value indicates an upright image

Lenses

  • Piece of glass or other transparent material takes on appropriate shape, it's possible that parallel incident rays would either converge to a point or appear to be diverging from a point

Refraction Rules

  • Converging Lens:
    • Any incident ray traveling parallel to principal axis of converging lens will refract through lens and travel through focal point on opposite side of lens
    • Any incident ray traveling through focal point on the way to lens will refract through lens and travel parallel to principal axis
    • Incident ray that passes through center of lens will in effect continue in same direction that it had when it entered lens
  • Diverging Lens:
    • Any incident ray traveling parallel to principal axis of diverging lens will refract through lens and travel in line with focal point (ex: in a direction such that its extension will pass through focal point)
    • Any incident ray traveling towards focal point on the way to lens will refract through lens and travel parallel to principal axis
    • An incident ray that passes through center of lens will in effect continue in same direction that it had when it entered lens

Lens Characteristics

  • Converging Lenses:
    • Light rays are converging to a point after refracting through the lens, real image is formed
    • Real image is formed whenever refracted light pass through image location
    • Converging lenses are capable of producing both real/virtual images
  • Diverging Lenses:
    • Always produce virtual images
    • Image will be located on the object side of lens
    • Image will be upright and reduced in size (smaller than object)

Dispersion

  • Visible/white light is a collection of component colors
  • Upon passage through prism, white light is separated into component colors (red, orange, yellow, green, blue, violet)
  • Prism is a transparent glass with 2 flat surfaces angled at an angle
  • Spectrum is a band of colors scattered by light entering glass prism
  • Causes of Dispersion:
    • Each color's light has a distinct wavelength
    • White light disperses to 7 colors because each color has a different wavelength
    • Red light has the longest wavelength, violet light has the shortest
    • In vacuum, all colors of light travel at the same speed

EM Waves

  • Waves transmit information/energy from one point to another in signal form
  • No material object makes this journey
  • Obtained by including time factor
  • Oscillation form through space/mass medium
  • Can travel through empty space; mostly invisible
  • 3 Wave Types:
    • Mechanical Wave: oscillation of matter and responsible for energy transfer through medium
    • Longitudinal wave: particle movement parallel to energy motion
    • Transverse wave: particle movement at right angles/perpendicular to energy motion
    • Combination of both longitudinal and transverse
    • Surface wave: particles travel in circular motion

Electromagnetic Spectrum

  • Properties and Formula:
    • Speed (c), frequency (f), wavelength (λ)
    • Wavelength/Frequency Relationship:
      • All parts of EM spectrum travel at the same speed
      • Wavelength and frequency have an inversely proportional relationship
      • Wavelength increases = frequency decreases
      • Wavelength, frequency, energy:
        • Short wavelengths = high frequency = high energy
        • Long wavelengths = low frequency = low energy
  • Notes:
    • EM waves don’t require media in which to travel or move
    • EM waves are transverse waves because they are made of vibrating electric and magnetic fields at right angles to each other, and to the direction waves are traveling

Reflection and Refraction

  • Reflection of Light:
    • Incident Ray vs Reflected Ray:
      • Incident ray: plenty of light rays reflect object from all directions
      • Reflected ray: light that bounced from surface and reached your eye
    • Reflection Law:
      • Incident ray, reflected ray, and the normal all lie in the similar plane called the plane of incidence
      • Incidence angle=reflection angle; regardless of wavelength or pair of materials
    • Reflection Types:
      • Specular reflection: when image is reflected from a smooth surface (specular means having properties of a mirror)
      • Diffuse reflection: reflection that happens on rough surfaces

Refraction of Light

  • Refraction: travels at a particular angle different refractive index into a medium/substance that has a refractive index (n)
  • Refractive index (n): light speed in free space : speed in given medium
  • Determined by optical density or "inert tendency" of material's molecules to keep absorbed energy of EM wave in form of oscillating electrons before releasing it back as a new disturbance
  • Measure of light ray bending as it travels from one medium to another
  • Snell's Law (Refraction Law):
    • Describes the relationship between the angle of incidence and refraction as light passes through 2 different media
    • n1sinθ1 = n2sinθ2
  • Common Refractive Indices:
    • Various light colors move at different rates in any transparent material (glass/water)
    • Various colors' lights bend through different angles due to differences in velocity
    • Red travels fastest, violet travels slowest
    • Thus, red light bends least, violet bends most
    • Thus, white light dispersion into 7 colors happens when various colored photons bend at different angles while passing through a glass prism
  • Visible Light Spectrum:
    • Optical density: measure of the tendency of material to slow down light as it travels through it
    • Tendency of atoms to maintain absorbed energy of light wave in form of vibrating electrons before reemitting it as a new EM disturbance
    • Snell's Law:
      • Light wave travels through a vacuum at a speed of c (3.00 x 10^8 m/s), it travels through a transparent material at a speed less than c
      • Index of refraction value (n): provides a quantitative expression of the optical density of a given medium
      • Materials with higher index of refraction values have a tendency to hold onto absorbed light energy for greater lengths of time before reemitting it to interatomic void
    • Angle of Deviation:
      • Amount of overall refraction caused by light ray passage is often expressed in terms of the angle of deviation
      • Angle made between the incident ray of light entering the first face of the prism and the refracted ray that emerges from the second face of the prism
    • Rainbow:
      • Example of white light dispersion
      • High # of tiny water droplets remain hanging in the air shortly after rain
      • Each drop functions as a tiny prism
      • When sunlight strikes these droplets, white light divides into 7 distinct colors

Review electromagnetic waves, including their properties, types, and characteristics. Learn about mechanical waves, oscillation, and energy transfer. Test your understanding of electromagnetic waves and their behavior.

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