Sometimes I have these moments when I just don't get something in Science... Or better yet, I get it but I don't know how to explain it. I was feeling very much like this when it came down to teaching the difference between reflection and refraction. We were doing reflection labs during the October PLC's and no matter how I looked at the activities, and how much I understood it myself, I couldn't get angle of reflection down so that I could explain it to my students easily.
Here was my dilemma... You see a reflection is the bouncing back of light and to my students, many of whom are second language learners, have problems processing language while at the same time processing new concepts. I didn't know how to explain to them the angle of reflection when I had just told them that refraction is when light bends. Now I had to tell them that that when light reflects it bounces back at an angle... (but isnt that like bending?) How do you tell them that the light is bouncing at an angle but only sometimes because if you are bouncing the light straight forward then the light comes straight back. How do you know which angle to teach them? It isn't a specific angle. My biggest concern was that when I asked for an explanation at the PLC, the best I got was... "well its an even angle..." or "its an angle that is evenly divided..." (what??!!!) That would just confuse them more... Somebody said, "well, just bounce a ball against the wall at different angles and it will bounce back at the angle of reflection..." Um, okay (I said getting out the wall ball out of my drawer...) Hmmmm....
At least, that was until I spoke to Monika Thomas who told me about this really cool activity that Sergio Peralta did for the kids at Moye Elementary.. With this activity you can teach angle of reflection in about 10 minutes with no fuss...
This is one of those labs that is so easy that even a caveman can do it...
Materials: Protractor, Flashlight or laser pointer, dry erase marker, mirror
Procedure:
1. Draw a straight line across the mirror with a dry erase marker making sure to divide the mirror evenly in half. Stand the mirror or have a student hold the mirror up on the table
2. Lay the protractor flat on the table with the flat end against the mirror, making sure that the middle of the protractor is aligned with the line drawn on the mirror
3. Using the laser pointer or flashlight, choose a marked degree on the protractor (say 80 degrees) shine the light from the 80 degree mark to the line in the middle of the mirror. The light will bounce back on the opposite side of the protractor at the opposite 80 degree mark... (way cool)
4. Now try pointing the light from the 50 degree mark to the middle of the mirror. The light will bounce back at the 50 degree mark on the other side of the protractor.
5. The beam of light is more concentrated in a laser pointer, so it is easier to see, but if you only have a flashlight here is a way to make sure that the kids understand that the light is pointing at that precise angle:
Have a student place a finger on the degree mark on the opposite end... example: if you are pointing the flashlight at 30 degrees, have them place their finger on the 30 degree mark on the opposite side of the protractor. The concentration of light will hit their finger at the angle of reflection and as they slide their finger to other points on the protractor the beam will no longer shine on their finger.
6. If you place the light at 90 degrees, the light bounces straight back with no angle (even cooler)
Thank you Sergio and Monika for sharing this with me, because my kids learned angle of reflection in 10 minutes and I didn't have to try to explain what the angles were with words... They got it!!
Enjoy-
Techscichick
p.s.
Sergio sent in these awesome pictures because seeing it for yourself is always better than reading about it.