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Microwaves and Infrared Waves

Microwaves and Infrared Waves

This lesson aligns with NGSS PS4.B

Electromagnetic waves transmit energy through matter or space as vibrating electric and magnetic fields. Electromagnetic waves have a wide range of wavelengths and frequencies. The complete range of these wavelengths and frequencies is referred to as the electromagnetic spectrum. The electromagnetic spectrum is divided into electromagnetic spectrum such as radio waves, microwaves, infrared waves, visible light, ultraviolet, x-rays, and gamma rays. Microwaves fall between the infrared and radio waves within the electromagnetic spectrum. In this article, we will explore what are microwaves and infrared waves, their properties, and their applications in our lives.

Microwaves are a type of electromagnetic radiation with wavelengths ranging from approximately one millimeter to one meter. They have shorter wavelengths and higher frequencies than radio waves. Therefore, microwaves carry more energy than radio waves. The key properties of microwaves are their ability to penetrate various materials and their efficient energy transfer to heat.

Microwave Oven
The most common use of microwaves is in microwave ovens, where they are used to cook and heat food quickly and efficiently. Microwaves penetrate the outer layers of food and heat the water molecules inside, resulting in even cooking. Let us see how the microwave oven works.

How Does Microwave Oven Work?
  • A device known as a magnetron generates microwaves through the acceleration of charged particles.
  • The microwaves bounce off the metal fan and are then directed into the cooking chamber.
  • Microwaves can penetrate several centimeters into the food.
  • The energy carried by microwaves induces vibrations in water molecules within the food.
  • These molecular vibrations cause the temperature of the food to increase.

Microwaves are also used in radar technology, also known as radio detection and ranging. Radar uses microwaves to detect the speed and position of the objects.

A police officer uses radar to determine the speed of the car on the road, as depicted in the figure. The officer points the radar device toward the car and activates it, causing the emission of short pulses of microwaves. These microwaves bounce off the car’s surface and return to the radar device. The rate at which the microwaves are bounced off is used to calculate the speed of the car.
Radar is also used in tracking the movement of airplanes and assisting ship captains in navigating at night or in foggy weather.

Infrared Waves
Infrared waves commonly known as infrared light, are part of the electromagnetic spectrum. People encounter infrared waves regularly. Although these waves are invisible to human eyes, humans can detect them as heat.

In comparison to microwaves, infrared waves possess shorter wavelengths and higher frequencies. Therefore, infrared waves can carry more energy than both microwaves and radio waves.

On a sunny summer day, when you sit outdoors, the warmth you feel  is a result of infrared waves emitted by the sun. Your skin absorbs these Infrared waves when they strike your body. The energy carried by these waves causes the particles in your skin, leading to faster vibrations, and you feel the increased vibration as an increase in temperature.

In addition to the sun, various sources emit infrared waves, such as stars, planets, buildings, trees, and even human beings. The quantity of infrared radiation released by an object varies depending on the object’s temperature. The warmer objects emit more infrared radiation than cooler ones.

As mentioned above, human eyes cannot see infrared waves, but some devices can detect infrared radiation. For instance, infrared binoculars convert infrared radiation into light you can see. Such binoculars are very useful to observe animals at night.

Applications of Infrared Waves
Thermal Imaging
Infrared cameras are widely used in thermal imaging applications. They detect infrared radiation emitted by objects and convert it into visible images. This technology is used in night vision, search and rescue missions, and monitoring building heat loss.

Remote Controls
Infrared is utilized in remote controls for various devices like televisions, air conditioners, and home entertainment systems. The signals emitted by the remote control are picked up by the device, triggering the desired action.

  • Microwaves are known as electromagnetic radiations with a frequency ranging between 300 MHz to 300 GHz.
  • Microwaves possess shorter wavelengths and higher frequencies than radio waves. Due to the shorter wavelength, they are suitable for radar technology to detect the speed and position of objects.
  • In comparison to microwaves, infrared waves possess shorter wavelengths and higher frequencies.
  • Infrared cameras are widely used in thermal imaging applications.

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