Physics EM waves

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Physics EM waves por Mind Map: Physics EM waves

1. Properties of EM waves

1.1. Transverse waves

1.2. Medium not required to propagate

1.3. Travel at 3.0x10^8

1.4. Reflection refraction

1.5. C=f 人

1.6. Non mechanical

2. EM spectrum

2.1. 1.Radio waves

2.1.1. Lowest frequency,longest wavelength

2.1.2. Eg. Remote control cars, walkie talkie

2.2. 2.Microwaves

2.2.1. Radio waves with short wavelength

2.2.2. When subjected to oscillating EM fields, highly polar water molecules rotate rapidly. Heat due to friction.

2.2.3. Eg. Mobile phones, microwave oven

2.3. 3.Infrared rays

2.3.1. Molecules vibrate/resonate easily. Heat waves

2.3.2. Night vision: amplification of ambient infrared rays. Ir waves to electric signals to visible light.

2.3.3. Thermal imaging: detect people with fever SARS h1n1

2.4. Visible light

2.4.1. Color determined by frequency or wavelength

2.4.2. Optical fibers,light photography

2.5. UV rays

2.5.1. Suntanning. Skin cancer overexposure

2.5.2. UV watermarks for security. Fluorescence effect special ink glow.

2.5.3. Passports credit cards

2.5.4. New Node

2.6. X rays

2.6.1. High frequencies high penetrating capability

2.6.2. Bones black cause absorb x ray.

2.6.3. X rays ionizing radiation chest x rays pose cancer risk

2.7. Gamma rays

2.7.1. Highest frequency ,most penetrating.

2.7.2. Emitted during radioactive decay of unstable atoms or isotopes or nuclear radiation.

2.7.3. Treat cancer patients by killing cancer cells. Side effects

2.7.4. Sterilization