Electromagnetic Spectrum Notes

Teachers' Domain: Tour the Electromagnetic Spectrum
Teachers' Domain: The Electromagnetic Spectrum: FRONTLINE
Teachers' Domain: Tour of the Electromagnetic Spectrum: Radio Waves

What are electromagnetic waves?

What is a photon?

Name one manufactured device or natural phenomenon that emits electromagnetic radiation in each of the following wavelengths: radio, microwave, infrared, visible light, ultraviolet, X-ray, and gamma ray.

Which type(s) of electromagnetic radiation do human bodies emit? Which type(s) can our senses detect?

List three ways that electromagnetic radiation is used to improve our everyday lives. 

============

Everybody has at some time thrown a pebble into a puddle and observed the ripples spreading across the surface.  Some of us don’t stop until the puddle has been completely filled with every loose piece of debris in the vicinity.  Now let’s dive in a bit deeper into the physics.

Select the Wave Interference simulation

1)      Before you change any settings

a.       What is the shape of the pulse?

b.      How can you explain this?  Talk about crests or frequency.

Reflection:

2)      Increase the amplitude to maximum.

3)      Turn off the water and add a vertical wall (bottom right button) across the entire width of the tank.

4)      Turn on the water for just a couple of drips.

5)      Observe the wave reflection from the barrier

a.       What is the shape of the reflection?

b.      In what ways does it differ from the incident (incoming) wave?

c.       Compare this result to what you learned about reflected pulses from the wave on a spring demo?

Interference:

6)      Allow the faucet to run.  Feel free to adjust the frequency.

a.      What do you think the particularly bright and dark spots represent?

7)      Show the graph and observe the last couple of waves in front of the wall.

a.       Once again, considering the wave on a spring demo, what do these last waves on the graph remind you of?

8)      A second example of wave interference can be seen by removing the barrier and turning on a second drip

a.       Draw or describe the resulting pattern.

b.      How are the dark & light stripes similar to and different from standing waves?  (Hint:  Look at the graph again)

c.       What do you think may be happening along the gray rays?

d.      How can you test your ideas?  Hint:  Consider the purpose of the horizontal dashed line.

e.       Perform the experiment.  Was your hypothesis supported or rejected?

9)      Adjust the drip frequency, pausing a few seconds for the image to stabilize after each change.

a.       How does drip frequency relate to the number of rays?

b.      What is the range for the number of rays you can generate?

c.       Is there a pattern?

10)  Return the frequency to full and double the drip spacing.

a.       Now how many rays can you count?