Dispersion of Light

Dispersion of Light Diagram

Understanding Light Dispersion

Dispersion is the phenomenon where white light splits into its constituent colors when passed through a prism. This occurs because different colors of light travel at different speeds in glass, causing them to refract at different angles.
Sir Isaac Newton was the first to demonstrate that white light is composed of colors. In 1666, he used a prism to split sunlight into the colors of the rainbow.

Welcome to the Dispersion of Light Interactive Module!

Select any option from the sidebar or buttons above to explore the concepts of light dispersion.

Key Idea: Dispersion of Light

Dispersion of Light Diagram

Core Concept

White light consists of seven colors (VIBGYOR - Violet, Indigo, Blue, Green, Yellow, Orange, Red). When passed through a glass prism, it splits due to different refractive indices for different colors.

Some Important Topics:

1. Refractive Index and its Dependence on Wavelength:

Definition: Refractive index (n) of a medium is the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v).

Formula: n = c / v

Dependence on Wavelength (also known as Dispersion): The refractive index varies with wavelength of light. Shorter wavelengths (like violet) are refracted more than longer wavelengths (like red). This phenomenon is called chromatic dispersion. Reason: Due to interaction of light with the medium's atoms; light of different wavelengths travels at slightly different speeds in the same medium.

Key Point: n(violet) > n(red)

Hence, violet light bends more than red light in a prism.

2. Angle of Minimum Deviation(δₘ):

Definition: It is the smallest angle through which light is deviated after passing through a prism. Concept: > As the angle of incidence increases, the angle of deviation first decreases, reaches a minimum, and then increases again. > This minimum value is called the angle of minimum deviation. Formula: n = (sin(A+δₘ)/2) / sin(A/2) Where: n = Refractive index of prism material A = Angle of the prism d𝑚 = = Minimum deviation angle Importance: Used in calculating the refractive index of the prism material experimentally.

3. Comparison between Prism and Grating Dispersion:

a. Working Principle: Prism: Refraction (based on Snell's Law) Diffraction Granting: Diffraction and Interference b. Wavelength Dependence: Prism: Non-linear dispersion Diffraction Granting: Linear dispersion c. Resolution: Prism: Lower (less sharp spectral lines) Diffraction Granting: Higher (better separation of wavelengths) d. Light Loss: Prism: More (due to absorption/reflection) Diffraction Granting: Less (more efficient in transmission) e. Dispersion Type: Prism: Angular dispersion by refraction Diffraction Granting: Angular dispersion by interference pattern f. Usefulness: Prism: Good for white light spectrum Diffraction Granting: Better for precise wavelength analysis

Scientific Explanation

The refractive index of glass is different for different colors. Violet light refracts the most while red light refracts the least. This difference in refraction angles causes the separation of colors.

Historical Context

Sir Isaac Newton was the first to demonstrate that white light is composed of colors. In 1666, he used a prism to split sunlight into the colors of the rainbow.
Newton's Experiment: Newton darkened a room and created a small hole in the shutter to allow a beam of sunlight to enter. He then placed a prism in the path of the light, causing it to separate into a band of colors (a spectrum).
Prior to Newton's work, it was believed that white light was a single, pure color and that other colors were created when white light was modified. Newton's experiment proved this theory wrong.

Real-world Applications

  • Rainbow formation
  • Spectrometers for chemical analysis
  • Optical fiber communications
  • Camera lenses (chromatic aberration correction)

Simulation: Dispersion of Light

Adjust the angle of incidence to see how it affects the dispersion of light through a prism.

Observations:

  • As the angle of incidence increases, the dispersion becomes more pronounced
  • Violet light bends the most, red light bends the least
  • The angle between red and violet rays is called the angular dispersion

Simulation Quiz

Test your understanding of light dispersion. Answer all questions and submit to see your results.

Quiz Results

Your Score: 0/0

Performance Analysis:

Key Concepts to Review:

    Recommendations:

    Based on your quiz performance, we recommend reviewing the following topics:

    • Refractive index and its dependence on wavelength
    • Angle of minimum deviation
    • Comparison between prism and grating dispersion

    Quiz Answers

    Check for Understanding

    Answer these questions to test your basic knowledge before proceeding to the simulation.

    Pre-Simulation Questions

    1. What is white light composed of?

    A. Single color

    B. Multiple colors

    C. Only primary colors

    D. No colors (it's transparent)

    2. What happens when white light passes through a prism?

    A. It gets absorbed

    B. It gets reflected

    C. It splits into different colors

    D. It becomes brighter

    3. Which color deviates the most when passing through a prism?

    A. Red

    B. Green

    C. Blue

    D. Violet

    Why Check Understanding?

    This pre-simulation assessment helps ensure you have the foundational knowledge needed to get the most from the interactive simulation. Research shows that students who engage with preparatory materials before simulations demonstrate better learning outcomes.

    Key Concepts to Review:

    • Nature of white light (composition of colors)
    • Basic principles of refraction
    • Relationship between light wavelength and refraction
    • Sequence of colors in dispersion (VIBGYOR)

    Simulation Activity: Exploring Light Dispersion

    Follow these guided activities to explore dispersion phenomena through interactive experimentation.

    Activity 1: Basic Dispersion Observation

    1. Set the angle of incidence to 45° using the slider
    2. Observe how white light splits into different colors
    3. Identify which color bends the most and which bends the least
    4. Record your observations in the table below
    Color Angle of Deviation Observation
    Violet -- --
    Red -- --

    Activity 2: Angle of Incidence vs Dispersion

    1. Set the angle of incidence to 30°
    2. Note the width of the spectrum produced
    3. Gradually increase the angle to 60° in 5° increments
    4. Record how the spectrum changes at each angle

    Activity 3: Critical Thinking Questions

    1. What happens to the spectrum when you set the angle of incidence to very low values (below 30°)? Why does this occur?

    2. If you could change the prism material, how would using diamond instead of glass affect the dispersion? Explain.