"The Fastest "Messenger"" Electromagnetic Waves and Information Age PPT Courseware

Description

"The Fastest "Messenger"" Electromagnetic Waves and Information Age PPT Courseware

learning target

1. Know what electromagnetic waves are

2. Know the characteristics of electromagnetic waves

3. Understand the application of electromagnetic waves in life

1. Experience electromagnetic waves

Activity 1: Electromagnetic waves around us

Turn on the radio, turn the tuning knob to no radio station, and then turn the volume knob to make the volume louder. Take a dry battery and a wire, first connect one end of the wire to one pole of the battery, and then rub the other end of the wire against the other pole of the battery. What's your reaction to listening to the radio? Why such a reaction?

The rapidly changing current stirs up electromagnetic waves in the space around it! So the radio will receive this electromagnetic wave and make noise!

The use of mobile phones has become widespread. Please think about: How do two mobile phones transmit information?

2. Understand electromagnetic waves

A large number of experiments have shown that when the current in a conductor changes rapidly or a high-frequency alternating current is passed through, the conductor will emit a wave to the surrounding space. Such waves are produced by electromagnetic phenomena and are called electromagnetic waves.

Conditions for the generation of electromagnetic waves: current changes rapidly in magnitude and direction

Electromagnetic waves are similar to water waves and sound waves. They have wave speed, frequency, and wavelength, and can also be described by waveform diagrams.

Wave crest: The highest point on the graph is the wave crest

Trough: The lowest point on the graph is the trough

①The distance between two adjacent wave crests (or troughs) is called wavelength. Expressed by λ, the international unit of wavelength is meter (m)

②The number of wavelengths that electromagnetic waves propagate forward per second is called frequency. Represented by f, the international unit of frequency is Hertz (HZ)

1KHZ=103HZ 1MHZ=106HZ

③The speed at which electromagnetic waves propagate is called wave speed. Represented by C, the international unit of wave speed is m/s

3. Application of electromagnetic waves

Based on their frequencies or wavelengths, people have weaved a "family tree" for this "family" - the electromagnetic spectrum.

There are many "family members" of electromagnetic waves. Each "member" has a different wavelength or frequency range, and each has its own characteristics. Therefore, electromagnetic waves are widely used.

Below we will learn about the characteristics and uses of different electromagnetic waves.

infrared

Infrared is a type of light wave whose wavelength is shorter than radio waves and longer than visible light. Approximately from 1mm to 700nm.

UV rays

Ultraviolet light is outside of purple light and has a wavelength range between 5 and 400nm, which is invisible to the human eye!

Features: High energy, can make fluorescent substances glow

visible light

The wavelength of visible light is between 700 and 400nm

Sunlight is composed of various colors of light. Different light wavelengths are different

X-ray

The wavelength of X-rays ranges from approximately 5nm to 0.01nm.

X-rays have a strong effect on living matter and can penetrate matter

gamma rays

The wavelength of γ rays is approximately from 0.01nm to 10-4nm, and it has high energy. Can destroy living matter. It can be used to destroy diseased cells and treat certain cancers. Its penetrating ability is also very strong. Can be used to detect defects inside metal parts.

summary

1. Electromagnetic waves can be used to transmit information in daily life.

2. Electromagnetic waves have wave speed, frequency and wavelength, and can also be described by waveform diagrams. The distance between two adjacent wave crests or troughs is called wavelength.

The number of wavelengths that an electromagnetic wave travels forward per second is called frequency. Electromagnetic waves can propagate in a vacuum at a speed equal to the speed of light

3. The relationship between electromagnetic wave speed, wavelength and frequency is:

C= λf C=3.0 × 108m/s

4. Different electromagnetic waves have different characteristics and different uses.

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"The Fastest "Messenger"" Electromagnetic Waves and Information Age PPT Courseware 2:

"The Fastest Messenger" Electromagnetic Waves and the Information Age PPT Courseware 2 Think about it. It is impossible to use wires to communicate between the pilots on the plane and the ground commanders, so how are they connected? We listen to the radio or watch TV every day, and there are no wires directly leading to the radio or...

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Update Time: 2024-10-01

This template belongs to Physics courseware Guangdong and Shanghai Edition Ninth Grade Physics Volume 2 industry PPT template

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