Saturday, November 27, 2010

Selecting a Microscope for the Kids or Grand kids

   The gift-giving season is here and if, as a grandparent or parent, you intend to purchase a microscope for your kids, then read on. The following information will not only save you money but also keep you from giving the kids a gift that can be the source of more frustration than educational fun.
   Microscopes, especially the ones sold in the major retail outlets, usually tout the high-power of the product. They often look like the microscope shown above. For kids untrained in microscope use, 50 power (50X) is more than enough magnification.
   Don't assume kids are being taught microscope skills in the elementary grades. Until kids have been taught how 'field of view' and 'depth of field' affect what's seen through a microscope, observing at higher powers will simply frustrate the kids. In a school system with a good science program, they may learn these skills in middle school. If they don't, let's hope they have a good biology teacher in high school. 
   When looking through a microscope, the lens near the eye is called the eyepiece lens and the lens at the other end of the tube, near the object being examined, is called the objective lens.

   The power of the lens-pair is computed by multiplying the power of the eyepiece lens by the power of the objective lens. These powers are stamped on the barrel of each lens. My favorite microscope, the Brock Magiscope (shown above), has a 10X (10 power) eyepiece lens and a 4X (4 power) objective lens. The magnifying power of the tube is therefore 10X x 4X or 40 power. That’s enough power to see the organisms in a drop of pond water.
   Remember, the higher the power, the smaller the field of view, the thinner the depth of field, and the more difficult it is to find and view an object through the microscope.
   A microscope that kids can actually use will provide lots of enjoyable hours viewing minuscule objects like Abraham Lincoln seated in his Memorial on the back of a penny or the fantastic creatures that swim and live in a drop of water.

   The microscope shown above can be purchased at these web sites.

Wednesday, November 24, 2010

Thanksgiving 2010

   Grandad science and grandmother math received a special Thanksgiving email treat. It’s the above picture of our two oldest grand kids, Joshua and Jordann, with a geometric model they made by sticking pieces of uncooked spaghetti into small marshmallows. During a visit earlier this year, we had made geometric models using toothpicks and raisins that they dipped into a soapy solution to see the surprising shapes formed on the models by the interacting soap films (see the April 2010 post). It’s heartening to know they remember how to make the models!
   Wishing everyone a warm and  happy Thanksgiving with family and friends.

Saturday, November 20, 2010

Image on the Edge

“All physicists use their heads, the best also think with their fingers.”
                    Dr. George Polya   

   In previous posts, we've looked at two ways to establish the fact that the image in a flat mirror appears to be as far into the mirror as the object is in front of the mirror. Here’s a third method and one that kids like to do. Once you've gathered the materials, show the kids or grand kids how to setup and do the investigation (as illustrated and described below) and then let the kids view the video and repeat the investigation.

Plane mirror with binder clip (or anything else to hold the mirror upright)
Two, tall, identical objects
Sheet of paper

   As shown in the picture above, use a ruler to draw a line parallel to the left edge of a sheet of paper. Mark the line in inches. [Send an email to  and I will send you a pdf file of the ruled page as seen in the picture.]
   Attach the binder clip to the right edge of the mirror and place the mirror perpendicular to the ruled line at a point about halfway along the line. Place a tall object (like a AA battery or one of an identical set of salt and pepper shakers) on the ruled line so that half of its image is visible along the left edge of the mirror.
   Set the other object on the ruled line, behind the mirror. Your setup should look something like what’s seen in this picture.
   Observe that the half-image along the left edge of the mirror does not align with the object behind the mirror. The mirror image may appear to be behind or in front of the object.
   Slide the object behind the mirror, along the ruled line, until the image along the left edge of the mirror blends perfectly with the object.
   Compare the distances of the objects from the mirror line. When done accurately, the distances will be equal. As they say, “Seeing is believing.”
     Here is an animation I created that summarizes the on-edge method. It’s a short, 45-second video.

    With the holidays fast approaching. in the next post I will recommend the right microscope to purchase for your kids or grand kids.

Saturday, November 6, 2010

We Fly at iFly

   Joshua, our oldest grandson was born on Halloween. This year, for his tenth birthday, he wanted to go skydiving in a vertical wind tunnel.  There happens to be, within an hour from his home, a vertical wind tunnel. 
   Joshua’s mom and dad met at a drop zone where they both skydived. Dad was a skydiving instructor and mom ran the manifest where she kept the airplanes loaded with skydivers, and, when the paying customers were taken care of, went skydiving.
   Joshua’s dad arranged for all of us, grandadscience, grandmother math, and he and his family, to visit the iFly vertical wind tunnel near their home.
   The scientific principle used in the vertical wind tunnel is simple. Instead of a person falling through the air at 120 miles per hour, a big fan blows high-speed air upwards at and around a person.
   A ping-pong ball and your hair dryer will quickly demonstrate to you the feasibility of this method. Hold the hair dryer upright in one hand, turn it on to the highest setting, and drop the ping-pong ball it on the air stream. The ball, contained in the air stream, will float above the open end of the dryer. Watch this short, 20-second video to see how this works (with no one around to help me, I had to put the hair dryer in a stand so that I could take the video).
   The hair dryer video demonstrates two scientific principles; first, Bernoulli’s principle tells us that the pressure in an air stream is lower than the pressure outside of the stream. That’s what keeps the ping-pong ball centered. Second, the weight of the ball equals the force due to upward air flow. That keeps the ball suspended in the airflow.
   Watch this video to see Joshua take the place of the ping-pong ball in the iFly vertical wind tunnel. Towards the end of the video, his instructor takes him up to the top of the chamber.
   Well done Joshua! Now here’s Jordann, his sister, flying in the tunnel. 

  It was a great family outing and we are all excited to go again. In case you are curious, children as young as five, if genuinely eager to do so, are allowed to fly in the wind tunnel.
   As shown in the video, a qualified instructor is with you at all times. You may have noticed the instructor giving hand signals to the fliers. Two outspread fingers means drop your legs. Two curled fingers, lift your legs. Spread legs drive the flyer forwards and curled legs causes the flyer to back up. The basic tunnel flying skill is learning the correct leg and arm positions so as to stay centered in the airflow. Thumbs up means the body position of the flyer is correct.
   Joshua and Jordann, Here’s a Thumbs Up from mom and dad, grandadscience, and grandmother math!