Nature of Light Mrs. McNeill

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What do these movies have in common?

• Lightning and sparks are seen. These indicate the presence of an electric field.

• Electricity transfers are present.

• Metal is used to surround the electric fields formed.

Why Metal?• Most materials can be classified as a conductor

(conductors are typically metals) or an insulator • Metals typically have loosely bound electrons in their

atoms. When electrons enter the metal, other electrons are displaced and flow out of the metal.

• *Electric fields strength can represented by how close field lines are to each other.Field lines closer together represent a stronger field whereas lines further apart represent a weaker field.

•Van de Graff’s produce charge and relatively high voltages. Discharge from a Van de Graff is seen as sparks. The longer the spark the higher the voltage

The Electromagnetic Spectrum

Predator

The Electromagnetic Spectrum

Infrared

• Infrared (IR) radiation is part of the electromagnetic spectrum that has a wavelength longer than that of visible light (400-700 nm). Infrared radiation spans roughly three orders of magnitude (750 nm to 100 µm).

• It can be considered the ‘heat’ given off from a body (thermal radiation).

So what is the Predator seeing here?

The red areas represent regions that are warmer

The blue areas represent regions that are cooler

Uses of Infrared

What is Light?• Today, scientists recognize that light is not matter but energy.

It travels through empty space at a speed of 300,000 kilometers per second, which is the fastest speed possible in the universe. Light slows down slightly as it travels through air, liquid, and some solids.

Nature of Light Videos and Reading Passage• In Discovery Eduation please watch the videos under ENGAGE

and read the reading passage • Reading Passage:• You Light Up My Life • Videos:• Measuring the Universe • How Fast Does Sound Travel?• Light and Revealing Objects

• Define the vocab words and watch the animation as well as the video associated with each

• light, wave, reflection, transmission, absorption, radiation, wavelength

Answer the Lesson Essential Questions

• Lesson Essential Questions:• How does light travel? • How does light behave when it strikes a boundary?

How Does Light Travel?

• Light is a form of energy called electromagnetic radiation. It travels as a wave that consists of an electric field and a magnetic field. The wave travels through empty space in a straight line, or ray. Light rays can travel indefinitely through space, which is why we can see distant stars that are billions of kilometers away—and even farther.

How Does Light Behave When It Strikes a Boundary?• Light rays interact with different kinds of matter in different

ways. Transparent materials, such as air and clear cellophane, allow most light rays to pass through them. Translucent materials, such as wax paper, scatter most of the light as it passes through. Opaque materials, such as wood and metal, absorb some of the light rays that strike them and reflect other rays.

Under Elaborate• 2 Videos:• Laser Light• Light Energy• 3 Reading Passages:• Light Brights• You Light Up My Life• Shine On

Nature of Light— Common Misconceptions

• Light does not travel with any speed from one point to another.• Reality: Light moves from one point to another at a finite speed.

• A shadow is something that exists on its own. • Reality: Shadows are due to objects that do not allow light to

pass through them.• Light only travels in one direction.• Reality: Light travels out in all directions from its source.