AQA GCSE FOUNDATION PHYSICS - The Electromagnetic Spectrum

The Electromagnetic Spectrum

The electromagnetic (EM) spectrum is a range of all types of electromagnetic radiation, arranged in order of increasing frequency (and decreasing wavelength).

What are electromagnetic waves?

EM waves are a form of energy that travel through space at the speed of light. They are transverse waves, meaning that the oscillations of the wave are perpendicular to the direction of energy transfer.

• Electric field: Oscillates perpendicular to the direction of wave travel.
• Magnetic field: Oscillates perpendicular to the direction of wave travel and the electric field.

Properties of EM waves

• Frequency (f): The number of waves passing a point per second, measured in Hertz (Hz).
• Wavelength (?): The distance between two consecutive peaks or troughs of a wave, measured in meters (m).
• Speed (c): The speed at which the wave travels, constant for all EM waves in a vacuum (approximately 3 x 10^8 m/s).

The relationship between these properties is given by:

c = f?

The different types of EM waves

The EM spectrum is divided into different regions, each with its own unique properties and uses:

1. Radio waves:

• Lowest frequency: Long wavelengths (meters to kilometers).
• Uses: Broadcasting (TV, radio), communication (mobile phones, satellites), radar.

2. Microwaves:

• Higher frequency: Shorter wavelengths (centimeters to millimeters).
• Uses: Cooking (microwave ovens), communication (satellite communication), radar.

3. Infrared radiation:

• Higher frequency: Even shorter wavelengths (micrometers).
• Uses: Thermal imaging, remote controls, heating.

4. Visible light:

• Narrow range of frequencies: Visible to the human eye.
• Uses: Seeing, photography, lighting.

5. Ultraviolet (UV) radiation:

• Higher frequency: Very short wavelengths (nanometers).
• Uses: Tanning, sterilizing, detecting forgeries.

6. X-rays:

• Even higher frequency: Even shorter wavelengths (picometers).
• Uses: Medical imaging, security scanners, crystallography.

7. Gamma rays:

• Highest frequency: Shortest wavelengths (picometers to femtometers).
• Uses: Medical treatment (radiotherapy), sterilization, industrial applications.

Summary of EM Waves

Remember:

• All EM waves travel at the speed of light.
• The higher the frequency, the shorter the wavelength.
• The type of EM wave determines its use.