Examples of Interesting Objects

For starters, here is the surface of an ordinary piece of printer paper. This shows quite easily that it is not smooth at all. This is important for explaining why paper does not reflect light the same way a mirror does (diffuse vs. specular reflection).

The mint-flavored Mentos have a pitted surface. These little holes act as nucleation sites for bubbles to form in carbonated liquid.

The new $100 Bill is an excellent candidate for this tool. Many of its security features are only appreciable if you have a microscope. For example, the tiny security writing along the length of the feather, or the security threads that are thrown in to curb counterfeiting. Also, note that you can clearly see the color changing glitter is lain in different directions on each side. Shine a flashlight at the bill for best results. Don't miss the raised ink on the front of the bill, you can feel it with your finger, but only with a microscope can you recognize the very specific patterns that in the relief.

One of my favorite experiments is to hold it up to a computer screen and see the different pixels that are making the colors. The lens offers an excellent opportunity to study how the primary colors of light are combined to generate new colors. When looking at pixels, I recommend the Google.com logo.

You will be using a computer screen anyway and it is such a familiar sight that students find this investigation highly amusing. Also look at the black cursor with a white background, to learn how white light is made. While you are at google.com you might as well do an image search for specific colors, like pink, or brown and find out how they are made by mixing RGB.

Speaking of mixing colors, take a close look at an image in a text book and see that these pictures are not made from RGB, but rather the primary colors of ink, CYMK. Cyan, yellow, magenta, and black are unequally mixed to form the color desired. For example, cyan and yellow makes green. That they are not red, yellow, and blue, is sometimes a surprise. Note also how messy individual letters look close up.

Pretty much any grain or crystal will look very interesting microscopically. Take a closer look at your rock collection or – even easier – just take some condiment packets from your local restaurant.

Of course insects offer a wonderful venue for this lens.  Because the camera is mobile, you now can look at and photograph living insects more easily.  Nonetheless, I still enjoyed looking at my insect collection with the camera.

The Physics of the Lens

Using your cell phone as a microscope has advantages beyond just the fact that it helps you make and share videos and pictures. One of the best things is that your camera has an autofocus, which makes it easier to get the image. Also, since the lens is making a virtual image, you do not have to move the object oppositely to the direction you want the image to move (this is a major annoyance when using conventional microscopes).

The lens has a focal length of about 1cm. I found this by projecting a real image of my ceiling lights and by assuming that since the object distance is so much greater than the image distance, that the focal length is the same as the image distance ( 1/f = 1/d_o + 1/d_i ).

Paper.

Here are up-close pictures of Mentos candies.

The color-change glitter effect is from having different colors on each side. The raised/patterned ink shows off the liberty bell.

A computer screen seen up-close.

A CYMK print image of a red car, green bushes, and a blue sky.

A fly from a student's collection gets his close-up

James Lincoln
Tarbut V' Torah High School
Irvine, CA, USA

James Lincoln teaches Physics in Southern California and has won several science video contests and worked on various projects in the past few years. James has consulted on TV's "The Big Bang Theory" and WebTV's "This vs. That" and the UCLA Physics Video Project.

Contact: [email protected]