HOW NAPHTHALENE(MOTH BALL) WORKS?

Mothballs are small balls of chemical pesticide and deodorant used when storing clothing and other articles susceptible to damage from mold or moth larvae (especially clothes moths like Tineola bisselliella).
Their use when clothing is stored out-of-season gave rise to the colloquial usage of the terms "mothballed" and "put into mothballs" to refer to anything which is put into storage or whose operation is suspended.

Composition and safety

Older mothballs consisted primarily of naphthalene, but due to naphthalene's flammability, modern mothballs instead use 1,4-dichlorobenzene (also called para-dichlorobenzene, p-dichlorobenzene, pDCB, or PDB). Both of these ingredients have a strong, pungent, sickly-sweet odor often associated strongly with mothballs. 1,4-Dichlorobenzene and naphthalene should not be mixed, as they react chemically to produce a liquid which may cause damage to items being preserved.^[1] Camphor, an insect repellent, can also be used as a less-toxic ingredient in mothballs.
Both naphthalene and 1,4-dichlorobenzene sublimate, meaning that they evaporate from a solid state directly into a gas; this gas is toxic to moths and moth larvae.
For either of these insecticidal chemicals to be effective, they need to be placed with the clothing in a sealed container so the vapors can build up and kill the moths. In a sealed atmosphere like this, the vapors are not as harmful to people because they are relatively contained. The main exposures would occur when filling or opening the containers, or from wearing clothes immediately after opening (especially a problem for infants). A possible solution is to open the containers outside and let the clothes hang and air out for a day before wearing, though this practice will also expose the clothes to any moths that may be flying about, risking re-infestation.

Uses and risks

In addition to repelling or killing insects such as moths and silverfish, mothballs have been used as a stovepipe cleaner, snake repellent, and to keep away mice or other pests.^[2]
The main concern about the use of mothballs as a snake, mouse, or animal repellent or poison is their easy access to children, pets, and beneficial animals. Leaving them in a garden or in a living space unprotected makes it very easy for unintended victims such as children and pets to gain access to them. Mothballs are highly toxic when ingested (they have a sweet taste, making this more likely), and will cause serious illness or death. In addition to this, using a very large quantity of mothballs in a basement or a living space may cause serious respiratory problems in people living in the space.^[3]
Mothballs have been promoted as a squirrel repellent, and are an ingredient in some commercial repellent products. They are generally ineffective, and are no substitute for physical measures to exclude squirrels from building interiors.^[4]
Mothballs are a neurotoxin - especially those made of para-dichlorobenzene - and need to be treated as such. Mothballs have also been found to be carcinogenic.^[5]
Mothballs have been used for solvent abuse by adolescents, causing a variety of neurotoxic effects.^[6][7]
Older-formula mothballs have also been used by drag racers to enhance the octane value of fuel by dissolving the mothballs in some of the fuel and filtering out the remains with a filter paper. In the Mythbusters episode "Scuba Diver, Car Capers", it was shown to be "plausible" that adding mothballs to a car's fuel tank would increase its horsepower.

How Much Radiation Does Your Cell Phone Emit?

When we think about environmentally friendly cell phones, typically the first things that come to mind are their energy efficiency, the elimination of toxins in their manufacturing, their recyclability, or even what green apps we use. But what about their radiation emissions? The Environmental Working Group has released a website that sorts through cell phones and shows the emissions levels of over 1,000 cell phone models.
The group states, "Recent studies find significantly higher risks for brain and salivary gland tumors among people using cell phones for 10 years or longer. The state of the science is provocative and troubling, and much more research is essential. We at Environmental Working Group are still using our cell phones, but we also believe that until scientists know much more about cell phone radiation, it's smart for consumers to buy phones with the lowest emissions."
And so, they've released a Cell Phone Radiation Guide. You can look up your model of phone, check out the phones with the least and most emissions, read through available research, and find out how to reduce your exposure levels.
They also encourage users to take action on the issue, providing a form for people to fill out that encourages the FCC and FDA to require emissions information on phones, and do anything possible to reduce emissions in the first place.
It's not exactly a call to fashioning a tin foil hat to strap on every time you want to make a call, but it is a big awareness booster. Until we have more science around radiation emissions from cell phones, we might as well err on the side of caution. The Environmental Working Group's new database helps you do just that.

why does a boomerang come back?

Unlike an airplane or helicopter propeller, which starts spinning while the vehicle is completely still, you throw the boomerang, so that in addition to its spinning propeller motion, it also has the motion of flying through the air.
In the diagram below, you can see that whichever wing is at the top of the spin at any one time ends up moving in the same direction as the forward motion of the throw, while whichever wing is at the bottom of the spin is moving in the opposite direction of the throw. This means that while the wing at the top is spinning at the same speed as the wing at the bottom, it is actually moving through the air at a higher rate of speed.
When a wing moves through the air more quickly, more air passes under it. This translates into more lift because the wing has to exert more force to push down the increased mass. So, it's as if somebody were constantly pushing the whole spinning propeller of the boomerang at the top of the spin.

But everybody knows that when you push something from the top, say a chair, you tip the thing over and it falls to the ground. Why doesn't this happen when you push on the top of a spinning boomerang?
If you've read How Gyroscopes Work, then you may have already guessed what's going on here. When you push on one point of a spinning object, such as a wheel, airplane propeller or boomerang, the object doesn't react in the way you might expect. When you push a spinning wheel, for example, the wheel reacts to the force as if you pushed it at a point 90 degrees off from where you actually pushed it. To see this, roll a bicycle wheel along next to you and push on it at the top. The wheel will turn to the left or right, as if there were a force acting on the front of the wheel. This is because with a spinning object, the point you push isn't stationary, it's rotating around an axis! You applied the force to a point at the top of the wheel, but that point immediately moved around to the front of the wheel while it was still feeling the force you applied. There's a sort of delayed reaction, and the force actually has the strongest effect on the object about 90 degrees off from where it was first applied.
In this scenario, the wheel would quickly straighten out after turning slightly because as the point of force rotates around the wheel, it ends up applying force on opposite ends of the wheel, which balances out the effect of the force. But constantly pushing on the top of the wheel would keep a steady force acting on the front of the wheel. This force would be stronger than the counterbalancing forces, so the wheel would keep turning, traveling in a circle.
If you've ever steered a bicycle without using the handlebars, you've experienced this effect. You shift your weight on the bicycle so that the top of the wheel moves to the side, but every bicycle rider knows that the bike doesn't tip over as it would if it were standing still, but turns to the right or left instead.
This is the same thing that is happening in a boomerang. The uneven force caused by the difference in speed between the two wings applies a constant force at the top of the spinning boomerang, which is actually felt at the leading side of the spin. So, like a leaning bicycle wheel, the boomerang is constantly turning to the left or right, so that it travels in a circle and comes back to its starting point.