Science Fair Idea: Lens Simulator Made With Sand

We admit that our ideas for science fair projects, even though they are extremely interesting, sometimes get a little bit complicated. And occasionally they could be a little bit dangerous if the student isn’t paying attention. Even though I know you’ll be careful, your parents and teachers might get nervous if you’re using toxic chemicals or playing around with lethal high voltages.

So today we present an idea that is extremely simple to carry out and should have no safety objections. Almost any student should be able to put the whole project together in a single evening. And the only materials you need are a piece of paper, some sand, and a couple of wheels connected together with an axle. If you rummage through your toybox, you probably have a toy car that you can borrow the wheels from. If you don’t, there’s probably a suitable donor as close as the nearest dollar store.

With these supplies, you can do a demonstration of how light is affected by a lens. You put a layer of sand on the paper in the same shape as the lens you want to examine. Then, you put the paper on a slight slope and roll the wheels straight down into the “lens” made of sand. Just like light waves hitting a real lens, the path of the wheels will bend. They will start out going straight down, but upon hitting the “lens,” they will turn toward the focal point. If set up correctly, all of the “light rays” will converge on the focal point, no matter where they originate.

Your science teacher, of course, demands more than simply coming up with some clever demonstration. You also are expected to come up with things like a hypothesis and conclusion. There are many possibilities here. For example, if the lens is more convex (in other words, if it’s “fatter”), then it will cause more of a bend, and the focal point will be closer.

Or, you can compare two lenses: A convex lens and a concave one. Your hypothesis could be that the convex lens will bend them in, and the concave one will bend them out. Your experiment will prove that this is correct.

It’s late, and you need to finish the science project by tomorrow morning. I understand. Almost all of the information you need can be found at Wikipedia, including the two diagrams below, which you will be able to duplicate with your “lens”. The red lines will duplicate the path of your wheel. The left side of the picture is the uphill side.

And if you really want to impress your teacher, you can include two “lenses” and make a telescope, again, simply by following the Wikipedia diagram:

The photo at the top of the page comes from Popular Science, February 1937.

1947 Radio-Phono Service Call

If you think something untoward is happening in this picture from 70 years ago, then you’re wrong. This radio-phono serviceman is simply making an ordinary service call, and it was important for him to bring the right parts. This ad from Astatic reminds him that it was always best to use exact manufacturer replacement parts, and that was especially true when it came to phonograph pickup cartridges.

To keep a service call from getting out of hand, the serviceman was advised to carry in his service kit a wide variety of pickups.

The ad appeared in the February 1947 issue of Radio Maintenance.

SWL’ing 1957

Sixty years ago this month, the cover of the February 1957 issue of Popular Electronics showed this avid SWL tuning the foreign shortwave bands with her Hammarlund HQ-110 receiver.

She was able to tune in numerous English-language programs thanks to the extensive listing of broadcasts contained in the magazine. Among the selections was Radio Moscow as shown in the photo below of these comrades working the console.

Groundhog Day 1942: Last Prewar Automobile

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Seventy-five years ago today, America celebrated its first Groundhog Day of the war. But because of wartime censorship, the groundhog’s report was not made public. Here, the Chicago Tribune, February 2, 1942, announces that the reports will not be available.

During the war, weather reports could have proven useful to the enemy, and were largely prohibited. Newspapers were allowed to print the Weather Bureau’s official forecast, but no other commentary was allowed. Certainly, an accurate prediction of whether or not the country would endure another six weeks of winter would not be permitted, as this information would be vitally important to the enemy.

Broadcasters even had to be careful with any mention of the weather. For example, even sports announcers were supposed to refrain from giving the weather conditions affecting the game. With enough such reports, an enemy listener would be able to piece together conditions throughout the nation. The idea was simply to deprive them entirely of that possible source of information.

The requirements for broadcasters were printed in the January 19, 1942, issue of Broadcasting:

Weather reports for use on radio will be authorized by the United States Weather Bureau. This material is permissible. Confirmation should be obtained that the report actually came from the Weather Bureau. Special care should be taken against inadvertent references to weather conditions during sports broadcasts, special events and similar projects.

Information concerning road conditions, where such information is essential to safeguarding human life, may be broadcast when requested by a Federal, State or municipal source.

Groundhog Day 1942 also saw the end of prewar auto production, as the U.S. auto industry geared up for war. The photo at the top of the page is the last automobile to be produced until the war ended. This gray Buick rolled off the assembly line at 1:31 PM, February 2, 1942, as shown in the February 16, 1942 issue of Life magazine.

The groundhog at work during peacetime.

1927 Popular Mechanics Crystal Set

Ninety years ago, the February 1927 issue of Popular Mechanics showed how to put together this simple but effective crystal set.

The cost of the parts (not including the headphones) was less than a dollar. The set was particularly recommended for boy builders, but as shown in this picture of grandmother enjoying a listen, the grown ups would also enjoy it.

The spiderweb style coil was wound on a cardboard form, and included a slider on one of the spokes for tuning. The crystal holder was mounted on top, and the wiring was neatly recessed into the wooden base, which called for a coat of mahogany or walnut stain. For best results, a 75-80 foot outdoor antenna was recommended, with a good ground to a cold water pipe. The set was said to provide good volume on local stations, with good selectivity.

1942 Farm Sets for Emergency Use

A month after Pearl Harbor, civilian radios were still being produced. The War Production Board was created on January 16, 1942, and issued its order on March 7, for consumer radio production to cease on April 22. During those intervening months, there was uncertainty as to the availability of both radios and parts, but both production and advertising continued, but with the War clearly in mind.

Later in the War, the availability of B batteries became an issue. In fact, numerous construction articles, such as this one from 1943, focused on how to make a battery set work on household current. But in the early days of the war, there was a demand for battery operated sets, since it was believed that there might be blackouts and the AC power wouldn’t be available.

This is apparent from the Radiola ad shown above from the January 1942 issue of Service magazine. Directed at dealers, the ad shows two “farm set” models, suitable for use with batteries on farms that had not been electrified. This ad suggested a new market for such sets, as an emergency set “that stays on when the power goes off.” It also suggested that electrification might be delayed in some areas due to the war.

The ad noted that one of these sets could be the best of both worlds. An optional accessory was the RCA model CV-42 “Electrofier” which would allow either of these sets to operate on household current. So there was a market for these sets even in town: The owner could run it off household current, but quickly switch over to batteries during a blackout.

NM Public Health Nurse’s Radio, 1943

US Farm Security Administration/Office of War Information photo.

Taken in January 1943, this photograph shows a Peñasco, New Mexico public health nurse relaxing with the radio in her quarters after dinner. According to the photo’s caption, “the radio is the only contact with the outside world. Papers come rarely to the town, and the nurse (identified in other photos as Marjorie Muller) at the clinic operated by the Taos County cooperative health association must depend on the news broadcasts to follow daily events.” She served at the clinic shown at right.

The radio is Zenith model 6G-601-M, as revealed by the distinctive sailboat design on the speaker grill. You can see a well preserved example at this link. The set was similar in circuitry and styling to the Transoceanic, but covered the broadcast band only. You can see and hear a nicely preserved specimen of the radio at this video:

The six tube portable (3Q5GT, 117ZG, 1LH4, 1LF, 1LN5, 1LA6) could run off 110 volt household current or batteries. It’s almost certain that the set was being run off batteries, since it seems very unlikely that the clinic had electric power. This and other photos show a kerosene lamp, and there’s no evidence of electric wires in any of the photos. The clinic did have a telephone, as shown in another photo in the collection.

The radio’s dial is tuned to just below 900 kHz. An antenna is visible coming out the window in the picture here of Nurse Muller outside her residence. According to the 1943 White’s Radio Log, there don’t appear to be any powerful West Coast stations near that frequency. But it was night, she had a powerful receiver and an outdoor antenna, and it’s likely that she was listening to WLS in Chicago on 890 kHz. If that’s the case, it’s possible she was listening to NBC Blue Network news with Earl Goodwin at 7:00 Central War Time, which would be 6:00 P.M. in New Mexico.

The photographer for all of the photos shown here was Farm Security Administration/Office of War Information photographer John Collier, Jr. More of his photos of the clinic are available at the Library of Congress website.

1917 Life Buoy

A hundred years ago this month, the cover of the January 1917 issue of Popular Mechanics showed this life buoy design for sheltering 40 passengers. According to the manufacturer, the design, made entirely of steel, was unsinkable, noncollapsible, and would ride upright in the roughest sea. The buoy was designed to be kept on deck, and if there were no time to launch it, passengers could simply get inside and wait for it to float free when the ship sunk.

An observer could sit in the conning tower and display lights or other distress signals through the window. A storage battery provided current for lights and fan, and there was space for storing water and provisions for ten days.

The bottom of the buoy was filled with cement for ballast, and the buoy weighed 2000 pounds.

SS Kansan, 1917

Within a few months, America would be at war, but a hundred years ago this month, the country was still neutral, and the cover of the January 1917 issue of Electrical Experimenter magazine showed how electricity was helping to preserve that neutrality.

The ship depicted is the steamer Kansan, of the Hawaiian-American line. The flag was painted on both sides of the ship, and powerful electric lights were employed to cast their rays on the flag at night.

There had been cases of neutral vessels being sunk by submarine commanders not wanting to get close enough to a ship to make a positive identification of its nationality. The immense flag “would seem to be a very sure manner of indicating to any submarine commander as to just what ship he was dealing with.”

While the illuminated flag apparently protected the Kansan during American neutrality, she did not fare well after the country’s entry into the war. On July 10, 1917, she was sunk without warning by a submarine or mine two miles east of Kardonis Point (Belle Isle), France. Four men died in the attack.

High School Victory Corps: 1942

According to the caption of this 1942 Office of War Information photo, this Los Angeles high school student took her radio and code instruction seriously. She was a member of the high school Victory Corps of Polytechnic High School.

Elsewhere in the city, the student shown below was similarly taking her defense training seriously as part of the Victory Corps. She was the sharpshooter of the girls’ rifle team at Roosevelt High School. The caption of this photo notes that rifle practice was one of the phases of the Corps’ activities.

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