Optics and Electromagnetic Waves

Electromagnetic Waves

• Visible light is a small part of all electromagnetic waves.
• Electromagnetic waves result from vibrations between electric and magnetic fields.
• They don't require a medium and can travel through space.
• Speed in a vacuum: 300,000,000 m/s.

Types of Electromagnetic Waves

• Radio:
  • Use: AM/FM radio, TV signals, cellphones, radar, astronomy
  • Wavelength: > 1 cm
• Infrared (IR, heat):
  • Use: Remote controls, heat detection, physical therapy (heating)
  • Wavelength: 700 nm – 0.05 cm
• Visible:
  • Use: Human vision
  • Wavelength: 400 – 700 nm
• Ultraviolet (UV):
  • Use: Tanning/burning skin, sterilization, increases skin cancer risk
  • Wavelength: 10 – 400 nm
• X-rays and gamma rays:
  • Use: Medical imaging, cancer treatment, security equipment
  • Wavelength: < 10 nm

Scientific Notation

• Used for very large or small numbers.
• Two parts:
  • A number between 1 and 10.
  • A power of ten.
• Steps to convert to scientific notation:
  • Place a decimal after the first non-zero digit (from the left).
  • Multiply by the appropriate power of ten (based on how many places the decimal moved).
• Moving the decimal to the left results in a positive exponent.
• Moving the decimal to the right results in a negative exponent.

Examples

• 465 = 4.65 × 10^2
• 0.0032 = 3.2 × 10^{-3}

Practice

• 3400 = 3.4 × 10^3
• 35,500 = 3.55 × 10^4
• 0.015 = 1.5 × 10^{-2}
• 0.00075 = 7.5 × 10^{-4}
• 2,000,000 = 2.0 × 10^6
• 0.001 005 = 1.005 × 10^{-3}
• 0.000019 = 1.9 × 10^{-5}
• 69 = 6.9 × 10^1
• 21,000 = 2.1 × 10^4
• 654,000 = 6.54 × 10^5
• 0.147 = 1.47 × 10^{-1}
• 0.085 = 8.5 × 10^{-2}
• 1.23 = 1.23 × 10^0
• 580 = 5.80 × 10^2
• 0.000 15 = 1.5 × 10^{-4}
• 0.000 104 = 1.04 × 10^{-4}
• 100.2 = 1.002 × 10^2
• 65,300 = 6.53 × 10^4
• 0.000 000 000 3 = 3.0 × 10^{-10}