Light and Other E.M. Waves

Light is a transverse wave. – Travels perpendicular to the medium – Visible light is just 1 type of electromagnetic wave that is given off by stars like our sun Electromagnetic waves are transverse waves that are made of electric and magnetic fields which vibrate up and down.

Like other transverse waves, electromagnetic waves travel faster through less dense mediums. – This is because, as the waves travel up and down there is less matter to slow them down as they pass through the medium. – They all travel fastest through the vacuum of space, at a speed of 3 x 10 8 meters per second!

Since they all travel the same speed and we know: v = f λ – Larger wavelengths = lower frequencies – Shorter wavelengths = higher frequencies

E.M. waves with short wavelengths have high energy (more harmful) E.M. waves with long wavelengths have low energy (less harmful)

Here is the order of the electromagnetic spectrum from largest wavelength/smallest frequency (energy) to smallest wavelength/biggest greatest frequency (energy). 1) radio waves 2) microwaves 3) infrared 4) visible light 5) ultraviolet light 6) X-rays 7) gamma rays.

The Electromagnetic Spectrum8 Radio waves Lowest frequency (energy) waves; long wavelengths Includes FM, AM, radar and TV waves Wavelengths of m and longer Used in many devices such as remote control items, cell phones, wireless devices, etc.

The Electromagnetic Spectrum9 Microwaves Shorter wavelengths than radio, but longer than the others Wavelength 1 x m to 1 x m First used in radar, now used in communication, medicine and consumer use (microwave ovens)

The Electromagnetic Spectrum10 Infrared waves Invisible electromagnetic waves that are detected as heat Can be detected with special devices such as infrared goggles Used in heat lamps Higher energy than microwaves but lower than visible light

11 Visible Light This is the portion of the electromagnetic spectrum that human eyes can detect. Different frequencies of visible light produce different colors. Red is the lowest frequency and violet is the highest frequency. Just remember: – ROY G BIV (red, orange, yellow, green, blue, indigo, violet)

The Electromagnetic Spectrum12 Ultraviolet waves Higher energy than light waves, and smaller wavelengths Can cause skin cancer and blindness in humans Used in tanning beds and sterilizing equipment

MAP TAP The Electromagnetic Spectrum13 X-Rays High energy waves First discovered by Roentgen Used in medicine, industry and astronomy Can cause cancer

MAP TAP The Electromagnetic Spectrum14 Gamma rays Highest energy Blocked from Earth’s surface by atmosphere Destroy living cells, but can be used by doctors to kill cancer cells.

MAP TAP The Electromagnetic Spectrum15

MAP TAP The Electromagnetic Spectrum16 Time to think….. 1. Do E.M. waves move parallel or perpendicular to a medium? APerpendicular BParallel CSide-to-side D“P” waves

2. What is the relationship between frequency and wavelength? AProportional BInversely proportional CEqual DReciprocal

3. What does ROY G BIV mean? ARed, Orange, Yellow, Green, Blue, Indigo, and Violet BRefraction, Out-of phase, Yelling, Gamma, Bulb, Interference, and Viscosity CRight, Over, Yonder, Good, Behind, In, and Very DRode Island, Ohio, Yosemite, Georgia, Butte, Illinois, Virginia-the West one

MAP TAP The Electromagnetic Spectrum19 “A” for True or “B” for False 4. Can you actually see x-rays? 5. Red is more energetic than yellow. 6. Gama waves travels faster than radio waves. 7. Microwaves more dangerous than radio waves.

MAP TAP The Electromagnetic Spectrum20 Answers 1. Frequency and wavelength are properties of waves and since speed is constant for em waves, as frequency increases, wavelength decreases. 2. Spectrum is a continuum of all electromagnetic waves 3, ROY G BIV is the difference colors of the visible light in order of longest wavelength to shortest wavelength. 4. X-rays can not be seen, only the waves in the visible light portion are visible. 5. Yellow is higher energy than red because it has a shorter wavelength and higher frequency. 6. Both travel at the same speed, 3.0 x 10 8 (all E.M. waves travel at the same speed) 7. Microwaves have a higher frequency than radio and carry more energy.