Light Theory Overview: Particle and Wave

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Questions and Answers

What does the term 'Irradiance' refer to?

The number of watts hitting a finite area regardless of origin (correct)

Energy produced per unit area by a blackbody

The total radiant energy emitted by a point source

Radiant power per solid angle from an extended source

According to Wien's Displacement Law, what relationship exists between the peak wavelength of blackbody radiation and its temperature?

Peak wavelength is directly proportional to the fourth power of temperature

Peak wavelength increases as temperature increases

Peak wavelength is independent of temperature

Peak wavelength is inversely proportional to temperature (correct)

What does the Inverse Square Law imply about radiant flux from a point source as distance increases?

Radiant flux increases with the distance cubed

Radiant flux decreases with the square of the distance (correct)

Radiant flux remains constant regardless of distance

Radiant flux increases linearly with distance

Which law describes that the total power emitted per unit area by a black body is proportional to the fourth power of its temperature?

Stefan-Boltzmann Law Signup and view all the answers

What does 'Radiance' specifically measure?

Radiant power per unit area from an extended source in a solid angle Signup and view all the answers

What condition leads to maximum constructive interference in wave phenomena?

The extra path length is an integer multiple of the wavelength. Signup and view all the answers

How does increasing the number of slits in a multiple slit interference setup affect the interference pattern?

It narrows the peaks and increases the magnitude. Signup and view all the answers

What must be true for reflectance, absorbance, and transmittance according to the conservation of energy?

R(𝜆) + A(𝜆) + T(𝜆) = 1. Signup and view all the answers

Which type of polarization involves controlling the direction of vibration of electric fields?

Linear polarization. Signup and view all the answers

In ray tracing, what happens to rays that approach the thin lens parallel to the optical axis?

They exit through the focal point (f'). Signup and view all the answers

What is the unit of visible luminous power?

Lumen Signup and view all the answers

How is Luminous Intensity defined?

Radiant Intensity attenuated by the V-lambda curve Signup and view all the answers

What does illuminance measure?

The number of lumens per unit area Signup and view all the answers

Which of the following describes constructive interference?

Two waves on the same side combine to create a larger wave Signup and view all the answers

Which statement is true regarding coherent light sources?

They have the same wavelength and matched wavefronts Signup and view all the answers

What leads to the observation of interference from incoherent light sources?

When EM waves interfere with themselves under specific conditions Signup and view all the answers

What is the proper definition of Luminance?

Radiance attenuated by the V-lambda curve Signup and view all the answers

Which diffraction theory explains the behavior of waves when the distance to the image is small compared to the slit width?

Fresnel Signup and view all the answers

What is the primary characteristic of light as described by the particle theory?

Light travels in straight lines unless bent. Signup and view all the answers

Which equation represents the phase shift of a sine wave?

y = A sin(2πkx + θ) Signup and view all the answers

What does the index of refraction (n) represent?

The relative slowing of light in a medium. Signup and view all the answers

Snell's Law relates which of the following elements together?

Angles of incidence and refraction. Signup and view all the answers

What causes dispersion in a medium?

The variation of the index of refraction with wavelength. Signup and view all the answers

What is the relationship between wavelength and frequency in wave propagation?

Wavelength increases as frequency decreases. Signup and view all the answers

Radiant power, or radiant flux, is defined by which of the following?

Energy per unit time from a defined origin. Signup and view all the answers

What mathematical relationship do you use to calculate the speed of wave propagation?

Speed = Frequency × Wavelength. Signup and view all the answers

The radiant intensity is associated with which of the following concepts?

Energy exiting a source. Signup and view all the answers

What is the unit of frequency?

Hertz (Hz) Signup and view all the answers

Study Notes

Particle Theory of Light

The particle theory of light was developed by Isaac Newton and others.
Light travels in straight lines unless it is refracted by lenses or prisms.
The pinhole camera provides empirical evidence of light traveling in straight lines.
Einstein's experiment using photons to knock electrons off a metal surface solidified the particle nature of light.

Wave Theory of Light

Light can also be described as a wave, similar to a sound wave.
Light waves are transverse waves, meaning the oscillations are perpendicular to the direction of motion.
Light waves have electric and magnetic fields that oscillate perpendicular to the direction of propagation (E, B, and K).
The wavelength of a light wave is the distance between two consecutive peaks.
The spatial wave number (k) describes the number of waves that repeat over a physical distance.
The phase shift of a sine wave is represented by theta.
A wave can also vary with time (y=Asin(2(pi)vt + theta)).
Frequency is measured in Hertz (Hz).
The period (T) is the inverse of the frequency (v).
The full equation of a wave is y=Asin(2πkx−2πνt+𝜙).

Speed and Index of Refraction

The speed of propagation of a light wave is calculated using the equation: speed=frequency x wavelength.
The speed of electromagnetic radiation in a vacuum is approximately 3x10^8 m/s.
Light travels slower in a medium and varies with the wavelength, frequency, and environmental variables.
The index of refraction (n) describes how much light slows down in a medium, n = c/v, where c is the speed of light in a vacuum.

Dispersion

Dispersion is the variation of the index of refraction with wavelength.
Normal dispersion occurs when shorter wavelengths slow down more than longer wavelengths.

Radiant Power and Irradiance

Radiant Power (Φ) is the total energy passing through a defined space per unit time.
It is measured in J/s or Watts (W).
Irradiance is the incident EM energy measured in W/m^2.
Radiance (L) is the measure of radiant power per unit area from an extended source in a 1sr cone.
It is measured in W/m^2 sr.
The inverse square law states that the total radiant flux in a given solid angle from a point source is a constant.

Visible EM Sources

Objects heated to a high temperature emit radiation.
A blackbody gives off radiation at all wavelengths and has a continuous spectrum.
The peak wavelength of blackbody radiation is inversely proportional to temperature (Wien's Displacement Law).
The total power per unit area emitted by a blackbody is proportional to the fourth power of its temperature (Stefan-Boltzmann Law).

Photometry

The human eye is not equally sensitive to all wavelengths of light.
Photopic Response Function (V-lambda) describes how the human eye perceives brightness across the EM spectrum.
Radiometry becomes photometry when it is adjusted to account for the V-lambda curve.
The lumen (lm) is the unit of visible luminous power.
Luminous intensity (Iv) is the measure of radiant intensity attenuated by the V-lambda curve.
It is measured in lm/sr or candela (cd).
Illuminance (Ev) is irradiance attenuated by the V-lambda curve.
It is measured in lm/m^2 or lux.
Luminance (Lv) is radiance attenuated by the V-lambda curve.
It is measured in lm/m^2sr, cd/m^2, or nits.

Optical Interference

The double-slit experiment demonstrates that light has wave properties.
Diffraction patterns are created by structured geometric objects.
Interference occurs when two waves interact.
Constructive interference occurs when two waves on the same side combine, creating a larger wave.
Destructive interference occurs when two waves on opposite sides combine, resulting in a flat line.
Sustained interference occurs when light is stable and coherent, meaning it has the same wavelength and matched wavefronts.
Most light sources are incoherent.
Interference can be observed when EM waves interfere with themselves, such as in thin films or diffraction gratings.

Diffraction Theories

Fraunhofer diffraction theory applies to plane coherent sources and large distances D to the image compared to the slit width.
Fresnel diffraction theory better explains behaviors when D is small.
Maximum constructive interference occurs when the extra path length is an integer multiple of the wavelength.
Maximum destructive interference occurs at half-integer multiples of the wavelength.

Diffraction Grating

A diffraction grating has multiple slits in a small area.
It causes interference fringes to form in a pattern.

Polarization

Polarization is the direction of vibration of the electric fields in a light wave.
Types of polarization include linear and circular.

Reflectance, Absorbance, and Transmittance

Objects absorb, reflect, and transmit light differently.
These characteristics are properties of the object.
The sum of reflectance, absorbance, and transmittance is 1.

Scattering

Scattering occurs when light interacts with unordered geometries.
It can affect the amount of light transmitted or reflected.

Absorption

A chromophore is a molecule that absorbs light.

Goniophotometry

Goniophotometry is the measurement of light reflected from a surface at different angles.

Power of a Surface

The power of a surface is given by the equation P=(n2-n1)/r, where n2 is the index of refraction of the material entered, n1 is the index of refraction of the material exited, and r is the radius of curvature.

Ray Tracing

Ray tracing rules are used to determine the path of light rays through a lens.
Rule 1: rays parallel to the optical axis pass through the focal point (f').
Rule 2: medial rays pass through the center of the lens without deviation.
The thin lens equation is 1/f’ = 1/u + 1/v, where u is the object distance and v is the image distance.

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Description

Explore the fundamental concepts of light through both the particle and wave theories. This quiz covers the contributions of key figures like Isaac Newton and Einstein, as well as the characteristics of light waves and their behavior. Test your understanding of how light is viewed in different scientific contexts.