Nature of light : Concept, properties, Equation, Laws, FAQs & Numerical

Nature of light : Concept, properties, Equation, Laws, FAQs & Numerical

Introduction: Light is a form of electromagnetic radiation that can be seen by the human eye. It has properties of both waves and particles, which makes it unique. In this article, we will discuss the nature of light, including its concept, equation, laws, frequently asked questions, and some numerical examples.

Concept of Light: Light is a type of electromagnetic radiation that travels through space at a constant speed of approximately 299,792,458 meters per second (m/s). It is a form of energy that can be seen by the human eye and is responsible for our vision. The color of light that we see depends on its wavelength, with longer wavelengths appearing red and shorter wavelengths appearing blue or violet. Light can be emitted by a variety of sources, including the sun, light bulbs, and fireflies, among others.

Equation for Light: The equation that describes the relationship between the speed of light, wavelength, and frequency is known as the wave equation. The equation is given by:

c = λν

Where c is the speed of light (in meters per second), λ (lambda) is the wavelength (in meters), and ν (nu) is the frequency (in hertz).

The equation tells us that the speed of light is equal to the product of its wavelength and frequency. This means that as the wavelength of light decreases, its frequency increases, and vice versa. The speed of light is a fundamental constant of nature and is denoted by the symbol 'c.'

Laws of Light: There are three laws of light that govern its behavior. These laws are:

• The law of reflection: This law states that when a ray of light is reflected from a surface, the angle of incidence is equal to the angle of reflection. This law is important in understanding how mirrors work.

• The law of refraction: This law states that when a ray of light passes through a boundary between two different materials, such as air and water, the direction of the ray changes. The amount of refraction that occurs depends on the angle of incidence and the properties of the two materials.

• The law of superposition: This law states that when two or more waves of light meet, the resulting wave is the sum of the individual waves. This is known as interference and can result in either constructive or destructive interference.

Frequently Asked Questions:

Q: What is the nature of light?
A: Light is a type of electromagnetic radiation that can be seen by the human eye. It has properties of both waves and particles, which makes it unique.

Q: What is the speed of light?
A: The speed of light is approximately 299,792,458 meters per second (m/s).

Q: What is the equation for light?
A: The equation that describes the relationship between the speed of light, wavelength, and frequency is c = λν.

Q: What are the laws of light?
A: The laws of light are the law of reflection, the law of refraction, and the law of superposition.

• What is the speed of light in a vacuum? Answer: The speed of light in a vacuum is approximately 299,792,458 meters per second (m/s).

• What is the electromagnetic spectrum? Answer: The electromagnetic spectrum is the range of all types of electromagnetic radiation, from radio waves to gamma rays.

• What is the frequency of light? Answer: The frequency of light is the number of wave cycles that pass a given point per second, and is measured in Hertz (Hz).

• What is the wavelength of light? Answer: The wavelength of light is the distance between two successive points on a wave, such as the crest or the trough, and is measured in meters (m).

• What is the relationship between frequency and wavelength of light? Answer: The frequency and wavelength of light are inversely proportional, meaning that as one increases, the other decreases. This is expressed by the equation c = λf, where c is the speed of light, λ is the wavelength, and f is the frequency.

• What is the photoelectric effect? Answer: The photoelectric effect is the phenomenon where electrons are emitted from a material when light shines on it.

• What is the dual nature of light? Answer: The dual nature of light refers to the fact that light exhibits both wave-like and particle-like behavior, depending on the experiment being performed.

• What is the energy of a photon of light? Answer: The energy of a photon of light is directly proportional to its frequency, and is given by the equation E = hf, where h is Planck's constant.

• What is the color of light with the longest wavelength? Answer: The color of light with the longest wavelength is red.

• What is the color of light with the shortest wavelength? Answer: The color of light with the shortest wavelength is violet.

• What is a polarizer? Answer: A polarizer is a material that can selectively filter out light waves that are oscillating in a certain direction, allowing only waves that are oscillating in another direction to pass through.

• What is diffraction? Answer: Diffraction is the bending of waves around an obstacle, resulting in the spreading out of the waves.

• What is interference? Answer: Interference is the combination of two or more waves that are in the same place at the same time, resulting in either reinforcement or cancellation of the waves.

• What is a laser? Answer: A laser is a device that emits a beam of coherent light through the process of stimulated emission.

• What is a hologram? Answer: A hologram is a three-dimensional image that is created by the interference patterns of light waves.

• What is fluorescence? Answer: Fluorescence is the emission of light by a material after it has been excited by absorbing light of a different wavelength.

• What is bioluminescence? Answer: Bioluminescence is the emission of light by living organisms, such as fireflies and jellyfish.

• What is total internal reflection? Answer: Total internal reflection is the reflection of light at the boundary between two media when the angle of incidence is greater than the critical angle, resulting in all the light being reflected back into the original medium.

• What is refraction? Answer: Refraction is the bending of light as it passes through a medium with a different refractive index.

• What is polarization? Answer: Polarization is the orientation of the electric field vector of a light wave, and can be either linear, circular, or elliptical.

Numerical Example:

Let's say we have a beam of light with a wavelength of 600 nm (nanometers). We can use the wave equation to calculate its frequency:

c = λν ν = c/λ ν = 299,792,458 m/s / (600 x 10^-9 m) ν = 4.996524 x 10^14 Hz

So the frequency of the light beam is approximately 4.996524 x 10^14 Hz.

LIGHT WAVES: Principles, Laws, Properties, Numericals and FAQs

LIGHT WAVES: Principles, Laws, Properties, Numericals and FAQs

Principle of super position of waves: -

When two or more than two waves come to a particle of a medium together then the displacement of the particle will be equal to the vector sum of displacements due to different waves reaching to the point. The waves coming to the particle will be going further without any change in them. Let the displacement in the particle due to one wave be y₁ and it is y₂ due to the second wave. Then resultant displacement of the particle will be ‘y’. 

Frequency and amplitude of superposed waves will depend on

       

Frequency And Amplitude Of Superposed Wave Will Depend On

1)      Frequencies of waves coming.

2)      Amplitudes of waves coming.

3)      Phase difference between the waves coming.

4)      Direction of waves coming.

                                                                  Interference

    When two waves of equal frequency, equal velocity and going in a direction in a medium are having superposition then they produce effect of interference.

Interference Of Light Waves: -

Definition: -Redistribution of energy in light waves due to superposition of waves is said to be interference of waves. Or,  when two waves of equal frequency going in a medium in a direction with a velocity are having superposition they effect the energy distribution of each other. At certain point where the waves meet in  a phase the displacement or amplitude /of the particle becomes more or intensity of light will be more but at the other certain points where the waves meet in opposite phase displacement/ amplitude of particle reduces and intensity of light reduces. In this way the increases and decreases in energy of light at different points in medium due to superposition of waves is said to be interference of waves.

Types of interference: -

1) Constructive interference: - When the waves are superposed in a phase or displacement or intensity increases than it said to be Constructive Interference. 

2) Destructive Interference: -When the waves are superposed in a opposite phase or  displacement or intensity decreases than it said to be Destructive Interference. 

Condition for interference: -

1)      The waves coming for superposition must be from the coherent sources, the wave must meet in a phase or have constant phase difference.

2)      The waves coming for superposition must be having equal frequency, wavelength or velocity.

3)      The wave must be propagating in a medium in direction

4)      If the amplitude of waves are equal than the interference will be clear or distinct

5)      If the path difference between the wave for reaching to any point in the medium is complete multiple of l say l, 2l, 3l, … ,nl or the phase difference between the waves is 0,2p,4p,6p,…  or  T, 2T, 3T,… then the point will be point of constructive interference.

6)      If the path difference between the waves reaching to a point is odd multiple of l/2, say l/2 ,3l/2, 5l/2,… ,(2n+1)l/2 or the phase difference is p,3p, 5p … or T/2, 3T/, 5T/2,…then the point will be destructive interference

Mathematical Analysis of interference 

Consider the waves having the same frequency and going along the x direction. Let the amplitude of the waves be a₁ and a₂ the phase difference between them is  f  then the wave equation will be

y₁ = a₁ sin wt

y₁ = a₁ sin (wt ± f)