Applications of the Doppler Effect with light

1. The Electromagnetic Spectrum

• The electromagnetic spectrum consists of all forms of electromagnetic radiation.
• Electromagnetic waves have both electric and magnetic components and are transverse waves.
• Examples: Light, radio waves, X-rays, gamma rays.
• Electromagnetic radiation does not need a medium to travel through (unlike sound waves)

2. The Doppler Effect in Light

a) Redshift – Object Moving Away

• When a star or galaxy moves away from Earth, its light shifts to longer wavelengths (lower frequency).
• This shift towards the red end of the spectrum is called redshift.
• Indicates that the universe is expanding (supports the Big Bang Theory).

b) Blueshift – Object Moving Closer

• When a star or galaxy moves towards Earth, its light shifts to shorter wavelengths (higher frequency).
• This shift towards the blue end of the spectrum is called blueshift.

3. Importance in Astronomy

✔ Determines the motion of stars and galaxies relative to Earth.

✔ Confirms the expansion of the universe (Hubble's Law).

✔ Helps scientists study distant celestial objects and their movement.

Exam Tip

💡 Remember:

• Redshift = Moving away = Lower frequency.
• Blueshift = Moving closer = Higher frequency.