Physics of Light and Electromagnetic Spectrum

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Questions and Answers

What did Max Planck hypothesize about the energy of radiation?

Energy is emitted in discrete portions called quanta (correct)

Energy varies with the size of the wave

Energy cannot be quantified

Energy is emitted continuously

What is the relationship between wavelength and energy of radiation?

Longer wavelength results in higher energy

Wavelength and energy are unrelated

Shorter wavelength results in higher energy (correct)

Only visible light has a defined wavelength-energy relationship

What is the value of Planck's constant?

3.14159 x 10^-34 J * sec

9.81 x 10^-34 J * sec

1.602 x 10^-10 J * sec

6.626 x 10^-34 J * sec (correct)

If a quantum of radiation has a frequency of 500 THz, which of the following represents the formula used to calculate its energy?

E = h * f Signup and view all the answers

What does the speed of light in a vacuum approximate to?

2.998 x 10^8 m/sec Signup and view all the answers

What type of waves does light consist of?

Transverse waves Signup and view all the answers

What is the formula for calculating wavelength ($\lambda$) of a wave?

$\lambda = v/f$ Signup and view all the answers

What does the electromagnetic spectrum encompass?

All kinds of electromagnetic waves Signup and view all the answers

Which of the following statements about electromagnetic (EM) waves is true?

EM waves travel at the speed of light in a vacuum. Signup and view all the answers

Which of the following colors of visible light has the longest wavelength?

Red Signup and view all the answers

What phenomenon occurs when light shines on a material and dislodges electrons?

Photoelectric Effect Signup and view all the answers

How is white light characterized in relation to the visible spectrum?

It consists of all wavelengths in the visible spectrum. Signup and view all the answers

Which of the following colors corresponds to the shortest wavelength in the visible spectrum?

Violet Signup and view all the answers

What happens to light when it strikes a surface that is not reflected?

It is transmitted or absorbed. Signup and view all the answers

What is the relationship between the angle of incidence and angle of reflection on a smooth surface?

The angle of incidence equals the angle of reflection. Signup and view all the answers

What does the percentage of absorption of light depend on for non-transparent surfaces?

The angle of light beam and wavelength. Signup and view all the answers

In terms of mirror reflectors, what is crucial when precise light control is required?

The efficiency of the mirror reflectors. Signup and view all the answers

What occurs when light strikes a red surface?

It reflects red light but absorbs most other colors. Signup and view all the answers

What kind of beam patterns can be produced when manipulating a light source and mirror shape?

Different beam patterns. Signup and view all the answers

What happens to light that is absorbed by a non-transparent surface?

It converts to heat energy. Signup and view all the answers

Which statement best describes transmission in relation to transparent materials?

Part of the light passes through these materials. Signup and view all the answers

What are the primary colors of light?

Red, Green, Blue Signup and view all the answers

What is the result of additive color mixing with red and green light?

White Signup and view all the answers

Which of the following is NOT a secondary color?

Green Signup and view all the answers

What is the outcome when cyan, magenta, and yellow pigments are mixed?

Black Signup and view all the answers

Which color is produced when red light mixes with blue light?

Magenta Signup and view all the answers

What does the CIE chromaticity chart plot?

Proportions of R, G, and B Signup and view all the answers

Which statement about subtractive color mixing is true?

It uses primary colors to create secondary colors. Signup and view all the answers

Which color wavelength is the human eye most sensitive to?

Green-Yellow Signup and view all the answers

In additive color mixing, what do you get when you mix yellow light with blue light?

Green Signup and view all the answers

Which of the following correctly states the formula for a color composition in the CIE chromaticity chart?

r + g + b = 1.0 Signup and view all the answers

What does the Colour Rendering Index (CRI) measure?

The accuracy of a light source in rendering colors Signup and view all the answers

What is the maximum value of the Colour Rendering Index?

100 Signup and view all the answers

According to the U.S. EPA Green Lights program, what CRI range is considered good?

65 - 75 Signup and view all the answers

Which colors can be considered primary colors when creating secondary colors?

Red, Green, Blue Signup and view all the answers

Which of the following describes the CRI rating of a light source with a rating of 0?

Poor color rendering Signup and view all the answers

What is the relationship between CRI and color temperature in lighting?

Both CRI and color temperature determine how colors are perceived Signup and view all the answers

What factor is most influential in night vision?

Rods Signup and view all the answers

What indicates that human vision is most sensitive to yellow-green wavelengths?

The peak response of the human eye Signup and view all the answers

Study Notes

Physics of Light

Light is electromagnetic radiation and travels in all directions from its source
Unlike sound waves, light waves consist of perpendicular electric and magnetic fields
Known as Transverse Waves
Wavelength (λ) is calculated using the equation: λ = v/f, where v is the velocity and f is the frequency of the wave
Wavelength is measured in nanometers (nm)
EM waves can travel through a vacuum, empty space, and through matter
Energy is not transferred through vibration, but rather through electromagnetic radiation
Speed of an EM wave is dependent upon the material it travels through
Speed of light in a vacuum is constant

The Electromagnetic Spectrum

The electromagnetic spectrum is the complete range of EM waves
Visible light only represents a small band of the electromagnetic spectrum
White light is a mixture of all wavelengths in the visible spectrum
White light can be separated into its components by a prism
Violet wavelengths are between 380 and 435 nanometers
Blue wavelengths are between 435 and 500 nanometers
Green wavelengths are between 500 and 565 nanometers
Yellow wavelengths are between 565 and 600 nanometers
Orange wavelengths are between 600 and 630 nanometers
Red wavelengths are between 630 and 780 nanometers

Wave-Particle Duality and the Photoelectric Effect

Electrons are emitted when light shines on a material, known as the Photoelectric Effect
Max Plank hypothesized that light exists as discrete wave packets
Electrons become dislodged when wave-like particles strike the surface

Electromagnetic Quantum Theory

In 1900, Max Plank assumed that energy of radiation is emitted in discrete indivisible portions called quanta
Photons are used to describe visible radiation
The energy content of a quantum of radiation is directly related to its frequency or wavelength: E = h * f or E = h * c / λ
E is energy measured in Joules, f is frequency measured in Hertz, h is Plank’s constant (6.626 x 10-34 J * sec), c is the speed of light in a vacuum (2.998 x 108 m/sec), and λ is wavelength measured in meters
Shorter wavelengths have higher energy, such as UV rays, X rays, and gamma rays

Interaction of Light and Surfaces

When light strikes a surface, it can be transmitted, reflected, refracted, or absorbed

Reflection

On a smooth surface, the angle of incidence (θi) is equal to the angle of reflection (θr)
High efficiency mirror reflectors are used when precise light control is required
Different beam patterns can be produced depending on the shape of the mirror and the position of the light source

Transmission and Absorption

For non-transparent surfaces, light that appears to ‘disappear' is absorbed and converted to heat energy
The percentage of absorption depends on the angle of the light beam and the wavelength

Color: Primary Colors

White light is a mixture of colors
Primary colors are Red, Green, and Blue
Secondary colors are Cyan, Magenta, and Yellow

Color: Additive Color Mixing

Additive color mixing is the mixing of light
Yellow, Magenta, and Cyan are made from a mixing of two primary colors
Complementary Colors are Yellow, Magenta, and Cyan
Red, Green, and Blue make White
Mixing a complementary color with the appropriate primary color makes White

Color: Subtractive Color Mixing

Subtractive color mixing is the mixing of pigments
Mixing colored paints always results in a darker shade than the original paints
Cyan, Magenta, and Yellow make Black
Subtractive mixing of complementary colors makes primary colors

Color: Spectral Power Distribution

The human eye is most sensitive to green-yellow wavelengths

Color: CIE Chromaticity Chart

Any color can be made using red (R), green (G), and blue (B) primary radiations
One unit of color can be matched by r proportion of (R), g proportion of (G) and b proportion of (B) such that: r + g + b = 1.0
The CIE chromaticity chart plots the proportions of X, Y, and Z in terms of x and y coordinates

Color: Color Rendering Index (CRI)

The CRI is a number between 0 and 100, indicating how accurate a light source is at rendering colors
A CRI of 100 means that the light source is a perfect match to a standard incandescent lamp
CRI is associated with the quality of lighting
A CRI of 75 - 100 is excellent
A CRI of 65 - 75 is good
A CRI of 55 - 65 is fair
A CRI of 0 - 55 is poor
CRI and the color temperature of a lamp determine how colors will be seen under that lamp

Summary

Light can be described as both electromagnetic waves and as wavelike particles (photons)
Visible light is a very narrow band of the electromagnetic spectrum
White light contains all the colors in the visible spectrum
Snell's Law can be used to determine the direction of propagation for refracted light rays
Light hitting a surface can be either reflected, refracted, transmitted, or absorbed
Cones are used for day vision (photopic) and rods are used for night vision (scotopic)
Visibility factors affect vision.
Secondary colors can be created from primary colors (Red, Green, and Blue)
There are two methods for specifying light colors: CIE chromaticity chart (x,y,z) and Correlated Color Temperature (CCT)
Human vision is most sensitive to yellow-green wavelengths
The Color Rendering Index (CRI) indicates how accurately a light source renders colors

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Description

Explore the fascinating world of light as electromagnetic radiation. This quiz covers the characteristics of light waves, their measurement, and the electromagnetic spectrum, including the process of light dispersion through a prism. Test your knowledge on these fundamental concepts of physics.