Posted by David Wetzel
Law of Reflection
Light behaves in a very predictable way. If a ray of light is observed approaching and reflecting off of a flat mirror, then the behavior of the light acts in a predictable manner. The diagram below illustrates the Law of Reflection.
Law of Reflection
In the diagram, the ray of light approaching the mirror is known as the incident ray. The ray of light which leaves the mirror is known as the reflected ray .
At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror. This line is known as a normal line (labeled N in the diagram).
The normal line divides the angle between the incident ray and the reflected ray into two equal angles. The angle between the incident ray and the normal is known as the angle of incidence.
The angle between the reflected ray and the normal is known as the angle of reflection.
The law of reflection states that when a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection.
Inquiry-Based Investigation
Materials: 30 cm of aluminum foil per student
Procedures:
- Students lay the aluminum flat on a table, shiny side up.
- Students lean over the aluminum foil to a point where they see their reflection and record their observations.
- Students wrinkle the aluminum foil (however not too much).
- Students now repeat step 2 and record their observations.
Student Questions:
- What did you see in the aluminum foil in step 2?
- What did you see in the aluminum foil in step 4?
- Why do you think you no longer see your reflection in step 4?
- What would you have to do so that you can see your reflection again in step 4?
Other questions based on student responses to these questions. Twenty questions to ask students provides additional examples of types of questions to ask students.
Types of Reflection
Reflection off of smooth surfaces such as mirrors or a calm body of water leads to a type of reflection known as specular reflection.
Reflection off of rough surfaces such as wrinkled aluminum foil, clothing, and paper leads to a type of reflection known as diffuse reflection.
Posted by David Wetzel
Hundreds Chart
There are many ways to use a hundred chart to help students develop a better understanding of math concepts, along with making connections within and between concepts.
When students see patterns or are able to connect math concepts in different and challenging settings, they truly understand and not just memorized math facts.
In addition to developing a better understanding of math concepts, students develop long term strategies for problem solving.
Five Ways to Use a Hundred Chart
I have come up with five ways to use a hundreds chart:
- Addition and Subtraction - Use the hundred chart as a number line to do addition and subtraction. Let the students challenge each other or the class to solve number line problems. One example is to add or subtract the fives first by counting up or down and then counting left or right.
- Multiplication - Look for counting-by multiplication patterns. Colored disks or other small manipulatives work well for marking numbers. Mark the numbers you hit when you count by four. What pattern do they make? Make the counting-by six pattern, or mark the sevens, etc. You may want to print several charts so you can color in the patterns and compare them. Some questions to ask include:
- Fractions, Percent, Decimals - The hundred chart can be used to convert between fractions, decimals, and percents. “Percent” means “out of 100.” So 30% means “30 out of 100″—which is how much of the whole chart? Some questions to ask include:
- Factors & Multiples - The first player marks any number on the hundred board. His/her opponent marks a factor or multiple of that number. Players alternate, each time marking a factor or multiple of the last number played. The player who marks the last number, leaving his opponent with no move, wins the game.
- Race to 100 - Take turns rolling one or two dice and moving that many spaces on the hundreds chart. If you correctly predict your landing place before you move (without counting squares!), then you can go one extra space as a bonus. The first person to reach or pass 100 wins the game.
Other Ways to Use a Hundred Chart?
Ideas or recommendations for additional ways to use a hundred chart to help students develop a better understanding of math, along with developing problem solving skills?
Comments:
Filed Under: Math
Posted by David Wetzel
Virtual Chemistry Lab
Here’s your chance to mix chemicals without wearing safety goggles. You won’t spill any acid on the spectrometer in this lab.
Choose solutions from the vast database and mix ‘em together till the cloned cows come home. Marvel as the chemical solutions react in real time.
Sample Simple Virtual Experiment
- Student goes to virtual workshop site (see below), open a new workbench (File>select New Workbench (Cntl-N).
- Then select Tools>Glassware>Beakers>600 ml Beaker.
- After the Beaker appears, using the LEFT mouse button, drag the beaker to the center of the work bench.
- Then RIGHT click and Select “Set as Recipient”.
- Select from the Stockroom Explorer (left hand side of screen) Distilled Water, using the Left Mouse button DRAG the water container onto the Workshop bench.
- Right click on the distilled water container and then select “set as Source”.
- Notice that the water container moves over your beaker.
- At the bottom of the workbench screen, look for the box next to “TRANSFER AMOUNT mL”. Type in 100, and then click the POUR button.
- Observe that 100 mL of water has been added to your beaker.
- Note down the Solution Info on the right hand side of the workbench. The pH is neutral (as demonstrated by equal concentrations of -OH and +H ions).
- Select Tools>Bunsen burner.
- After the Bunsen burner appears, using the LEFT mouse button, drag the Bunsen burner to a location under the beaker.
- Click on the Bunsen burner with the LEFT mouse burner and two arrows, one up and one down, appears on the right side.
- Click on the up arrow using the Left mouse button, this increases the size of the flame under the beaker.
- On the right side above the pH meter, the temperature increases from 25 degrees Celsius to 100 degrees Celsius (specific heat of water)
- Next observe that the pH of the boiling water drops to a pH of 6, down from a pH of 7.
This is a simple experiment to get a feel for how to operate the virtual chemistry lab.
Resource
Virtual Chemistry Lab Workshop
