5.4 Electromagnetic Waves

Physics Essential Standards Covered:

Phy.2.2.3

Compare mechanical and electromagnetic waves in terms of the following:
- - - how they are produced,
    - wave speed,
    - type of material (medium) required,
    - motion of particles,
    - patterns for refraction related to medium,
    - reflection,
    - interference,
    - the Doppler effect.

Key Vocabulary:

Electromagnetic Waves
Wave speed
Medium
Reflection

Lesson:

Electromagnetic Waves!

Waves where the electric fields and magnetic fields combine to create a wave. In the 1860's and 1870's, a Scottish scientist named James Clerk Maxwell made this connection and came up with what is now known as the "Maxwell" equations. (you don't need to know how to use these, just that they exist.)

Notice above how the different waves move.

Sound is a longitudinal wave and it's energy is transferred in the same direction of motion.

Mechanical waves are transverse waves and their energy is transferred perpendicular to the direction of motion.

Electromagnetic waves are a combination of transverse waves that oscillate back and forth between electric and magnetic fields.

Because the electric and magnetic fields are not constrained by any medium and can be everywhere, Electromagnetic waves are the only waves that can travel through space (without a medium to travel through).

Question!

Would the sound wave and the light wave from the sun be the same wave?

How long does it take for light from the Sun to reach the Earth if the distance between the Earth and the Sun is 148,980,000,000 m and the speed of light is 3.00 x 10^8 m/s?

t = (148,980,000,000 m)/(3.00 x 10^8 m/s)

t = 496.6 s or 8.28 minutes

How much longer would it take for the sound of the Sun to reach the Earth if sound could travel through space like air with a speed of sound being 343 m/s?

t = (148,980,000,000 m)/(343 m/s)

t = 434,344.023.32 s = 7,239.067.05 m = 120.651.12 hr = 5,027.13 days = 13.77 years

And it would be loud!

Electromagnetic Spectrum:

Scientist determined that there were several different types of electromagnetic waves with different frequencies and wavelengths and decided to create the electromagnetic spectrum.

Electromagnetic waves with long wavelengths and short frequencies have less energy. Electromagnetic waves with short wavelengths and fast frequencies have lots of energy. Electromagnetic waves with higher energy are called ionizing electromagnetic waves. They have the ability to transfer their energy to tiny particles which cause the particles to become ionized. These ions can then cause damage to DNA. X-ray's and Gamma rays are ionizing radiation and are used in cancer therapy because they damage DNA

Isn't it Ironic that Radiation that can cause cancer is used to kill cancer? This is solely because ionizing radiation can cause DNA damage and cell death. If you want cancer cells to die, kill them with ionizing electromagnetic radiation!

Fun Fact! All electromagnetic waves are considered radiation. However, not all are types of electromagnetic radiation are ionizing. That is because we have low energy electromagnetic waves too.

Next time you cook your burrito in the microwave tell you parents and siblings that you are irradiating your burrito. They will look at you like you are crazy!

Or the next time you drive to school or work and listen to the radio, think about how you are listening to radiation!

Ever wonder why after you get sunburned it still hurts and when you physically touch it it feels hot, but your body feels freezing? Well cause radiation! The harmful UVA and UVB rays have actually deposited their energy into your skin and you actually have that extra energy in your skin still cooking you! That is why your sunburn feels hot. You didn't wear sunscreen which actually helps reflect (wave behavior!) those harmful radiation waves away from your skin.

So those of you who "Tan" or use tanning lotion, you are actually "cooking" your self in the sun! Damaging your skin cells, eventually making them mutate and replicate giving you melanoma cancer when you get old and wrinkly!

Electromagnetic Radiation is all around us all day long every day! The only electromagnetic waves we can see are visible light. The rest you can't see and the high energy waves can actually travel through you! OUCH!

Don't worry, not all electromagnetic waves are bad. And don't believe this 5G stuff the internet keeps lying about.

Cell phones use radio waves to transmit their signals. Radio waves and microwaves which are non-ionizing radiation which does not damage DNA!

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5.4 Electromagnetic Waves

Physics Essential Standards Covered:

Key Vocabulary:

Suggested Reading:

Lesson:

Electromagnetic Waves!

Waves where the electric fields and magnetic fields combine to create a wave. In the 1860's and 1870's, a Scottish scientist named James Clerk Maxwell made this connection and came up with what is now known as the "Maxwell" equations. (you don't need to know how to use these, just that they exist.)

Notice above how the different waves move.

Sound is a longitudinal wave and it's energy is transferred in the same direction of motion.

Mechanical waves are transverse waves and their energy is transferred perpendicular to the direction of motion.

Electromagnetic waves are a combination of transverse waves that oscillate back and forth between electric and magnetic fields.

Because the electric and magnetic fields are not constrained by any medium and can be everywhere, Electromagnetic waves are the only waves that can travel through space (without a medium to travel through).

Question!

Would the sound wave and the light wave from the sun be the same wave?

How long does it take for light from the Sun to reach the Earth if the distance between the Earth and the Sun is 148,980,000,000 m and the speed of light is 3.00 x 10^8 m/s?

t = (148,980,000,000 m)/(3.00 x 10^8 m/s)

t = 496.6 s or 8.28 minutes

How much longer would it take for the sound of the Sun to reach the Earth if sound could travel through space like air with a speed of sound being 343 m/s?

t = (148,980,000,000 m)/(343 m/s)

t = 434,344.023.32 s = 7,239.067.05 m = 120.651.12 hr = 5,027.13 days = 13.77 years

And it would be loud!

Electromagnetic Spectrum:

Scientist determined that there were several different types of electromagnetic waves with different frequencies and wavelengths and decided to create the electromagnetic spectrum.

Isn't it Ironic that Radiation that can cause cancer is used to kill cancer? This is solely because ionizing radiation can cause DNA damage and cell death. If you want cancer cells to die, kill them with ionizing electromagnetic radiation!

Fun Fact! All electromagnetic waves are considered radiation. However, not all are types of electromagnetic radiation are ionizing. That is because we have low energy electromagnetic waves too.

Next time you cook your burrito in the microwave tell you parents and siblings that you are irradiating your burrito. They will look at you like you are crazy!

Or the next time you drive to school or work and listen to the radio, think about how you are listening to radiation!

So those of you who "Tan" or use tanning lotion, you are actually "cooking" your self in the sun! Damaging your skin cells, eventually making them mutate and replicate giving you melanoma cancer when you get old and wrinkly!

Electromagnetic Radiation is all around us all day long every day! The only electromagnetic waves we can see are visible light. The rest you can't see and the high energy waves can actually travel through you! OUCH!

Don't worry, not all electromagnetic waves are bad. And don't believe this 5G stuff the internet keeps lying about.

Cell phones use radio waves to transmit their signals. Radio waves and microwaves which are non-ionizing radiation which does not damage DNA!