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Electromagnetic Waves: Exploring Light, Infrared, and Microwaves in A-Level Science
What Are Electromagnetic Waves?
Electromagnetic waves are oscillations of electric and magnetic fields that travel through space without requiring a medium.
Properties of Electromagnetic Waves
Speed of Light (\( c \))
Electromagnetic waves travel at \( 3.0 \times 10^8 \, \text{m/s} \) in a vacuum:
\[
c = f\lambda
\]
Where:
- \( f \): Frequency (\( \text{Hz} \)).
- \( \lambda \): Wavelength (\( \text{m} \)).
Energy of a Photon (\( E \))
\[
E = hf
\]
Where \( h = 6.63 \times 10^{-34} \, \text{J·s} \): Planck’s constant.
Applications of Electromagnetic Waves
Light Waves
- Used in optics, lasers, and photography.
Infrared Radiation
- Employed in thermal imaging and remote controls.
Microwaves
- Essential for communication (Wi-Fi) and cooking.
Example Problem
Calculate the energy of a photon with a wavelength of \( 600 \, \text{nm} \).
- Formula:
\[
E = hf = h\frac{c}{\lambda}
\]
- Substitute Values:
\[
E = \frac{6.63 \times 10^{-34} \cdot 3.0 \times 10^8}{600 \times 10^{-9}} = 3.32 \times 10^{-19} \, \text{J}
\]
Common Mistakes in Electromagnetic Wave Problems
- Forgetting to convert wavelength to meters.
- Mixing up the energy formula for photons with classical energy equations.
- Ignoring the relationship between wavelength and frequency.
Practice Questions
- Calculate the frequency of a microwave with a wavelength of \( 0.1 \, \text{m} \).
- Explain how infrared radiation is used in thermal imaging.
- Describe one application of electromagnetic waves in communication.
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