PHY 04 Lesson 7: Light and its Identity

Optics

the branch of physics that studies the physical properties of light

James Clerk Maxwell

Scottish physicist who developed the theory of electromagnetism; showed that electricity, magnetism, and light are all manifestations of the electric field

Maxwell's Equation

a set of four fundamental laws expressed in mathematical form that govern electricity and magnetism and their interrelationship.

Gauss's Law for Electricity

Describes that the electric field due to electric charges can be derived by Coulomb's Law.

Faraday's law of electromagnetic induction

The induced e.m.f is directly proportional to the rate of change of magnetic flux linkage

Ampere's Law

An electric current generates a magnetic field that is proportional to the strength of the current. If the current is flowing in a coil of wire, the strength of the magnetic field is also proportional to the number of turns of wire in the coil.

Electromagnetic Wave

A wave that consists of oscillating electric and magnetic fields, which radiate outward at the speed of light

Oscilations

Movement back and forth of a regular speed

3x10^8 meters per second

Speed of light

Light

Combination of oscillating electric and magnetic fields that are perpendicular to each other.

Electromagnetic Energy

a form of energy that travels through space in the form of waves

Frequency, wavelength and speed

lambda

Wavelenght

Hz

Frequency unit

m

Wavelength unit

m/s

Speed unit

V

speed

Thomas Young

British physicist who studied light and devised the famous double-slit experiment that showed dual wave - particle nature of light

Double slit experiment

a demonstration that light and matter can display characteristics of both classically defined waves and particles

Longitudinal Waves

particles oscillate in the direction parallel to wave propagation

Transverse Wave

Particles oscillate perpendicular to wave propagation EX: LIGHT

Photoelectric effect

refers to the emission of electrons from a metal when light shines on the metal

de Broglie wavelength

Wavelength associated with a moving particle.

Wave-particle duality

the concept that all matter and energy exhibit both wave-like and particle-like properties

Rays

A straight line used to represent a light wave.

Proton

Form of energy visible to the human eye

tiny particle with EM radiation

No mass, no charge (neutral)

Travel at the speed of light

NO MASS=NOT MATTER

Fire

Matter because it is a mixture of different gases and takes up space

Heat

Level of vibration of matter, mostly atoms and molecules

Excited

Atoms with __________ electrons will emit PHOTONS and then LIGHT

EM Wave

Energy

Particles with photons

Wave-particle duality

rays

visible light

Light Characteristics

Reflection

the bouncing back of a ray of light, sound, or heat when the ray hits a surface that it does not go through

Law of Reflection

angle of incidence = angle of reflection

Specular Reflection

a reflection produced by a smooth surface in which parallel light rays are reflected in parallel

Diffuse Reflection

Reflection that occurs when parallel rays of light hit a rough surface and all reflect at different angles

Refraction

The bending of a wave as it passes at an angle from one medium to another

Variations in the speed of light through different materials

absolute index of refraction

the ratio of the speed of light in a vacuum to the speed of light in a medium

Snell's Law

n1sinθ1 = n2sinθ2

Mirrors

Form virtual images by reflecting light rays. No light actually comes from images.

Diffraction

The bending of a wave as it moves around an obstacle or passes through a narrow opening and illuminate areas where shadow is expected

Dispersion

White light separates into colors

Red

longest wavelength and lowest frequency

Isaac Newton

First person to obtain the spectrum of sunlight

The air molecules scatter blue light better than red light, so more blue light reaches our eyes.

Why the sky is blue

Rayleigh scattering

scattering of light caused by atmospheric particles smaller than the wavelength being scattered