# Light in Physics

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More Lessons for High School Physics

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A series of free Online High School Physics Video Lessons.

In this lesson, we will learn

• electromagnetic waves
• electromagnetic spectrum
• reflection and refraction
• Snell's Law
• double slit experiment

### Electromagnetic Waves

Electromagnetic waves are waves that take place in electromagnetic fields. When looking at electromagnetic waves in a vacuum, change in magnetic flux generate electric field and change in electric flux generates magnetic field. Alternating magnetic or electric field result propagation in vacuum in form of electromagnetic waves. The speed of the electromagnetic wave was found to be 3 × 108 m/s. Basic properties of electromagnetic are electric field and magnetic field perpendicular to one another in plane waves, the direction of propagation of is given by electric field × magnetic field, and the speed is calculated as wavelength times frequency
Understanding electromagnetic waves.

### Electromagnetic Spectrum

The electromagnetic spectrum depicts different frequencies of electromagnetic radiations shown from blue to red. On the electromagnetic spectrum, wavelength is shown to be increasing to the right and frequency is shown to be increasing to the left. The radiations in the order from blue to red on the electromagnetic spectrum are gamma, X-ray, UV, visible, IR, microwaves and radio waves with gamma being the smallest and radio waves being the biggest.
Understanding the different parts of the electromagnetic spectrum.

Electromagnetic Spectrum Song

### Reflection-Refraction

Reflection and refraction occur when a light hits a boundary between two media with different light speeds. When the light is split, part of it will be reflected and another part will be refracted. When dealing with refraction, the angle of refraction is determined by Snell's law. Total internal reflection occurs when there is a change in slow moving medium to a faster moving medium.

Demonstration of how light travels, Reflection and Refraction

### Snell's Law

Snell's Law is the quantitative way to analyze refraction.
Snell's Law is expressed in the formula
angle of refraction1 × sin (angle1) = angle of refraction2 × sin(angle2). This video introduces refraction with Snell's Law and the index of refraction. It also discusses why light bends when it strikes an interface at an angle. The second video discusses total internal reflection (TIR) in detail.
This video discusses total internal reflection (TIR) in detail.

This video demonstrates several Snell's law refraction problems.

### Double Slit Experiment

Double slit experiment, also known as the Young's experiment, was conduct by Thomas Young in 1803. This experiment confirms the wave nature of light, which is wave behaves as a wave, not a particle. Double slit experiment showed that two distances were formed by the slit. Constructive interference occurs when d(sin of the angle) = n(wavelength) and instructive interference occurs when d(sin of the angle)=(n+1/2)(wavelength).
The Double Slit Experiment
This video presents Young's Double Slit Experiment, the historical background that makes the experiment important, and a version of the experiment you can make on your own.

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