Question

What is the name given to the finite packets of light absorbed by matter?

Short answer

The name given to the finite packets of light absorbed by matter is 'photon.'

Step-by-step solution

Understanding Light Energy

Light energy is carried in discrete packets or units. These packets are considered the smallest unit of light and are involved in the transfer of energy when light interacts with matter.

Introducing the Photon

The term we use to describe these finite packets of light is 'photon.' A photon carries energy that is proportional to its frequency, and it does not have mass, traveling at the speed of light.

Defining Photons in Context

When matter absorbs light, it absorbs photons. Photons are fundamental to the electromagnetic theory of light, and their absorption can lead to various phenomena such as photoelectric effect or increasing the energy level of electrons within an atom.

Key concepts

Light Energy

Light energy is a type of energy that is visible to the human eye and is emitted by sources like the sun or light bulbs. It has a dual nature, behaving as both waves and particles. When it behaves as particles, it consists of tiny discrete packets called photons. Each photon is like a tiny bundle of light energy traveling through space. These photons carry energy that is directly related to the frequency of light; higher frequency light means more energetic photons, while lower frequency light means less energetic photons.

• Photons have no mass but carry energy.
• The energy of a photon is calculated using the formula: \( E = h u \), where \( E \) is energy, \( h \) is Planck’s constant, and \( u \) is the frequency of the light.

As photons strike matter, they can transfer their energy, initiating various interactions with the material.

Photoelectric Effect

The photoelectric effect is a captivating phenomenon observed when light, composed of photons, hits a material and causes electrons to be emitted from that material. This effect provided crucial evidence that light behaves as a particle rather than just a wave. For the photoelectric effect to occur, the photons must have enough energy to dislodge electrons from the material's surface. This is known as the threshold frequency.

• When light above a certain frequency hits a surface, electrons are ejected.
• If the frequency is below the threshold, no electrons are emitted regardless of the light intensity.
• Increasing the intensity of light increases the number of electrons emitted, but only if over the threshold frequency.

The discovery and explanation of this effect by Albert Einstein were pivotal in developing the quantum theory of light and won him the Nobel Prize in Physics in 1921.

Electromagnetic Theory

The electromagnetic theory describes how electricity and magnetism are interrelated and how they produce electromagnetic waves, which include light. According to this theory, light is an electromagnetic wave, a combination of oscillating electric and magnetic fields traveling through space. This wave phenomenon is crucial for understanding light’s behavior.Maxwell's equations, which form the foundation of electromagnetic theory, describe how electric charges and currents produce electrical and magnetic fields and how they propagate through space as electromagnetic waves.

• Electromagnetic waves move at the speed of light in vacuum, which is approximately \( 3 \times 10^8 \) meters per second.
• Light waves can be characterized by their wavelength or frequency, with each contributing to the type of light, such as visible light, ultraviolet, or infrared.

Photons play a critical role within this theory by being the particle representation of these electromagnetic waves, explaining how energy is transferred in quantized amounts.