waves can reflect refract! mrs. wolfe. have you ever heard an echo? ever wonder how blind bats can...
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What causes an echo? Sound waves hit objects and bounce back. Waves REFLECT! Can you think of an example for LIGHT waves reflecting?TRANSCRIPT
Waves can Reflect & Refract!
Mrs. Wolfe
Have you ever heard an echo?• Ever wonder how “blind” bats
can fly?• ECHOLOCATION!• They actually emit soundwaves.
These waves bounce off objects in front of the bat and the bat hears an echo.
• This tells them there’s something in front of them. No echo means they have a clear path!
Go to: http://science.howstuffworks.com/bat2.htm
What causes an echo?
• Sound waves hit objects and bounce back.
• Waves REFLECT!
• Can you think of an example for LIGHT waves reflecting?
Time for a Demo
• Let’s reflect a laser beam onto a mirror.
• What do you notice about the reflected light as compared to the incoming light?
Law of Reflection
• Waves bounce off a barrier at a specific angle.
• Angle of Incidence
• Angle of Reflection
• The angle of incidence is equal to the angle of reflection.
Practice Problem
• The angle made between the incident beam of light and the surface of the mirror is 25 degrees. What is the angle of REFLECTION of the light?
Let’s do an online lab and then a WS!
Waves can also REFRACT!
• Refraction is when waves BEND as the move from one medium to another.
• Demo:• Shine a LIGHT wave
through:– Corn syrup
Different Materials Bend Waves at Different Angles• Demo again:
– Corn Syrup, Vegetable oil, Water
• We assign these materials a number called its INDEX OF REFRACTION.*SEE HANDOUT!!
• High numbers mean waves are bent MORE!
• Which substance bends LIGHT the MOST?
When the wave changes mediums, it also changes SPEED!
• Higher index of refraction means SLOWER wave!
• Which material would transmit the SLOWEST wave?
So REFRACTION is…
• When waves change mediums, they BEND (change direction) AND CHANGE SPEED!
Let’s do an Online Lab and a WS!
Another Demo…The Disappearing Beaker!
• The inner beaker and the vegetable oil have the SAME INDEX OF REFRACTION.
• So as light moves from the oil to the glass of the inner beaker, the light does not reflect or refract. They haven’t really CHANGED mediums (indices of refraction).
• The result is that you can’t see the inner beaker!
Practice Problem
• When the boy throws the spear, he will miss the fish. Why?
Finally, when WHITE LIGHT REFRACTS….
• It separates into its individual colors:
ROY G BIV!
• Each wavelength of light bends at a different angle.
• DEMO TIME!• Let’s shine white light from
air into a prism.